Poly(vinyl acetal) resin compositions, layers, and interlayers having enhanced optical properties

ABSTRACT

Resin compositions, layers, and interlayers comprising two or more thermoplastic polymers and at least one RI balancing agent for adjusting the refractive index of at least one of the resins or layers is provided. Such compositions, layers, and interlayers exhibit enhanced optical properties while retaining other properties, such as impact resistance and acoustic performance.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Non-Provisional applicationSer. No. 14/587,702 filed Dec. 31, 2014, now pending, which claimspriority to U.S. Provisional Application Ser. No. 62/088,953 filed Dec.8, 2014, now expired, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field of the Invention

This disclosure relates to polymer resins and, in particular, to polymerresins suitable for use in polymer interlayers, including those utilizedin multiple layer panels.

2. Description of Related Art

Poly(vinyl butyral) (PVB) is often used in the manufacture of polymersheets that can be used as interlayers in multiple layer panels,including, for example, light-transmitting laminates such as safetyglass or polymeric laminates. PVB is also used in photovoltaic solarpanels to encapsulate the panels which are used to generate and supplyelectricity for commercial and residential applications.

Safety glass generally refers to a transparent laminate that includes atleast one polymer sheet, or interlayer, disposed between two sheets ofglass. Safety glass is often used as a transparent barrier inarchitectural and automotive applications, and one of its primaryfunctions is to absorb energy resulting from impact or a blow withoutallowing penetration of the object through the glass and to keep theglass bonded even when the applied force is sufficient to break theglass. This prevents dispersion of sharp glass shards, which minimizesinjury and damage to people or objects within an enclosed area. Safetyglass may also provide other benefits, such as a reduction inultraviolet (UV) and/or infrared (IR) radiation, and it may also enhancethe aesthetic appearance of window openings through addition of color,texture, and the like. Additionally, safety glass with desirableacoustic properties has also been produced, which results in quieterinternal spaces.

Often, polymers that exhibit one set of desirable properties, such asacoustic performance, lack other desirable properties, such as impactresistance or strength. Therefore, in order to achieve desirablecombinations of properties, multilayered polymer interlayers have beenused. These multilayered interlayers may include at least one inner“core” layer sandwiched between two outer “skin” layers. Often, the corelayer of an interlayer may be a softer layer having a lower glasstransition temperature, which enhances its acoustic performance.However, because such resin layers can be difficult to easily processand/or transport, the skin layers of such multilayered interlayers areoften stiffer, with higher glass transition temperatures, which impartsenhanced processability, strength, and impact resistance to theinterlayer.

However, use of various layers having different properties can alsoproduce optical defects within the interlayer. For example, one defectcommon to these types of multilayer interlayers is mottle. Mottle is anobjectionable form of optical distortion or visual defect appearing asuneven spots or texture, usually in the final structure. Mottle iscaused by small-scale surface variations at the interfaces between thesoft and stiff layers wherein the individual layers have differentrefractive indices. Clarity is another important optical property thatis determined by measuring the level of haze within the interlayer orpanel. High haze typically occurs when different types of opticallyincompatible polymers and/or plasticizers are blended or mixed together.In such mixtures, light passing through the blend is scattered as itencounters regions of different polymer materials, and the result is ahazy, visually unclear appearance. High clarity polymers and interlayersare those having very low haze values.

Thus, a need exists for polymer resins, resin layers, and interlayersthat exhibit desirable optical properties, such as reduced haze andmottle and improved clarity, without sacrificing other properties,including impact resistance and acoustic performance. Such interlayerscould be monolithic or multilayered and should be usable in a widevariety of applications, including safety glass and polymer laminates.

SUMMARY

In a first embodiment, the present invention is a blended resincomposition comprising: a first poly(vinyl acetal) resin componentcomprising a residual hydroxyl content; a second poly(vinyl acetal)resin component comprising a residual hydroxyl content; and at least onehigh RI plasticizer; wherein there is at least a 2 weight percentdifference in the residual hydroxyl content between said firstpoly(vinyl acetal) resin and said second poly(vinyl acetal) resin.

In a second embodiment, the present invention is a compositioncomprising: a blended poly(vinyl acetal) resin comprising: a firstpoly(vinyl acetal) resin comprising a residual hydroxyl content; asecond poly(vinyl acetal) resin comprising a residual hydroxyl content;and at least one high RI plasticizer, wherein the plasticizer has arefractive index of at least 1.460, wherein the refractive index of saidblended poly(vinyl acetal) resin is at least 1.480; and wherein there isat least a 2 weight percent difference in the residual hydroxyl contentbetween said first poly(vinyl acetal) resin and said second poly(vinylacetal) resin.

In a third embodiment, the present invention is a method for making aninterlayer, said method comprising: (a) providing a first poly(vinylacetal) resin or resin precursor comprising a residual hydroxyl content;(b) providing a second poly(vinyl acetal) resin or resin precursorcomprising a residual hydroxyl content; (c) blending said firstpoly(vinyl acetal) resin or resin precursor and said second poly(vinylacetal) resin or resin precursor and a high RI plasticizer to provide ablended plasticized poly(vinyl acetal) resin; and (d) forming at leastone resin layer comprising said blended plasticized poly(vinyl acetal)resin; wherein there is at least a 2 weight percent difference in theresidual hydroxyl content between said first poly(vinyl acetal) resinand said second poly(vinyl acetal) resin.

DETAILED DESCRIPTION

Resin compositions, layers, and interlayers according to variousembodiments of the present invention can comprise one or morethermoplastic polymers and a refractive index (RI) balancing agent. Asused herein, the term “refractive index balancing agent” or “RIbalancing agent” refers to any component or additive included in thecomposition, layer, or interlayer for adjusting the refractive index ofat least one of the resins or layers. The RI balancing agent mayincrease or reduce the refractive index of at least one of the resins orlayers within an interlayer, which may improve the optical properties ofthe interlayer, including mottle, haze, and/or clarity, as compared toan identical interlayer formed without an RI balancing agent.

As used herein, the terms “polymer resin composition” and “resincomposition” refer to compositions including one or more polymer resins.Polymer compositions may optionally include other components, such asplasticizers and/or other additives. As used herein, the terms “polymerresin layer” and “resin layer” refer to one or more polymer resins,optionally combined with one or more plasticizers, that have been formedinto a polymeric sheet. Again, resin layers can include additionaladditives, although these are not required. As used herein, the term“interlayer” refers to a single or multiple layer polymer sheet suitablefor use with at least one rigid substrate to form a multiple layerpanel. The terms “single-sheet” interlayer and “monolithic” interlayerrefer to interlayers formed of one single resin sheet, while the terms“multiple layer” and “multilayer” interlayer refer to interlayers havingtwo or more resin sheets coextruded, laminated, or otherwise coupled toone another.

The resin compositions, layers, and interlayers described herein mayinclude one or more thermoplastic polymers. Examples of suitablethermoplastic polymers can include, but are not limited to, poly(vinylacetal) resins, polyurethanes (PU), poly(ethylene-co-vinyl) acetates(EVA), polyvinyl chlorides (PVC), poly(vinylchloride-co-methacrylate),polyethylenes, polyolefins, ethylene acrylate ester copolymers,poly(ethylene-co-butyl acrylate), silicone elastomers, epoxy resins, andacid copolymers such as ethylene/carboxylic acid copoloymers andionomers thereof, derived from any of the previously-listed polymers,and combinations thereof. In some embodiments, the thermoplastic polymercan be selected from the group consisting of poly(vinyl acetal) resins,polyvinyl chloride, and polyurethanes, or the resin can comprise one ormore poly(vinyl acetal) resins. Although described herein with respectto poly(vinyl acetal) resins, it should be understood that one or moreof the above polymer resins could be included with, or in the place of,the poly(vinyl acetal) resins described below in accordance with variousembodiments of the present invention.

When the resin compositions, layers, and interlayers described hereininclude poly(vinyl acetal) resins, the poly(vinyl acetal) resins can beformed according to any suitable method. Poly(vinyl acetal) resins canbe formed by acetalization of polyvinyl alcohol with one or morealdehydes in the presence of an acid catalyst. The resulting resin canthen be separated, stabilized, and dried according to known methods suchas, for example, those described in U.S. Pat. Nos. 2,282,057 and2,282,026, as well as “Vinyl Acetal Polymers,” in the Encyclopedia ofPolymer Science & Technology, 3rd ed., Volume 8, pages 381-399, by B. E.Wade (2003). The resulting poly(vinyl acetal) resins may have a totalpercent acetalization of at least about 50, at least about 60, at leastabout 70, at least about 75, at least about 80, at least about 85 weightpercent, measured according to ASTM D-1396, unless otherwise noted. Thetotal amount of aldehyde residues in a poly(vinyl acetal) resin can becollectively referred to as the acetal component, with the balance ofthe poly(vinyl acetal) resin being residual hydroxyl and residualacetate groups, which will be discussed in further detail below.

According to some embodiments, the resin composition, layer, orinterlayer may include at least one poly(vinyl acetal) resin, which maybe present in the composition, layer, or interlayer in an amount of atleast about 0.3 percent, at least about 0.5, at least about 1, at leastabout 2, at least about 3, at least about 5, at least about 10, at leastabout 15, at least about 20, at least about 30, at least about 40, or atleast about 45 weight percent, based on the combined weight of allresins in the composition, layer, or interlayer. Together, the at leastone poly(vinyl acetal) resins can make up at least about 10, at leastabout 20, at least about 30, at least about 40, at least about 50, atleast about 60, at least about 70, or at least about 80 weight percentof composition, layer, or interlayer, based on the combined weight ofall resins. In some embodiments, the amount of resins other than the atleast one poly(vinyl acetal) resin can be not more than about 20, notmore than about 15, not more than about 10, not more than about 5, notmore than about 2, or not more than about 1 weight percent, based on thecombined weight of all resins.

In some embodiments, the resin composition, layer, or interlayer caninclude at least a first poly(vinyl acetal) resin and a secondpoly(vinyl acetal) resin, each of which may be present in thecomposition, layer, or interlayer in an amount of at least about 0.5, atleast about 1, at least about 2, at least about 3, at least about 5, atleast about 10, at least about 15, at least about 20, at least about 30,at least about 40, or at least about 45 weight percent, based on thecombined weight of all resins in the composition, layer, or interlayer.Together, the first and second poly(vinyl acetal) resins can make up atleast about 10, at least about 20, at least about 30, at least about 40,at least about 50, at least about 60, at least about 70, or at leastabout 80 weight percent of composition, layer, or interlayer, based onthe combined weight of all resins. In some embodiments, the amount ofresins other than the first and second poly(vinyl acetal) resins can benot more than about 20, not more than about 15, not more than about 10,not more than about 5, not more than about 2, or not more than about 1weight percent, based on the combined weight of all resins.

In some embodiments, one of the first and the second poly(vinyl acetal)resins can be present in the composition, layer, or interlayer in anamount of less than 12 weight percent, based on the combined weight ofthe first and second poly(vinyl acetal) resins. For example, the firstor the second poly(vinyl acetal) resin can be present in thecomposition, layer, or interlayer in an amount of at least about 0.5, atleast about 1, at least about 1.5, at least about 2, at least about 2.5,at least about 3, at least about 3.5, at least about 4, at least about4.5, at least about 5, at least about 5.5, at least about 6, at leastabout 6.5, at least about 7 weight percent and/or not more than about12, not more than about 11.5, not more than about 11, not more thanabout 10.5, not more than about 10, not more than about 9.5, not morethan about 9, not more than about 8.5, not more than about 8, not morethan about 7.5 weight percent, based on the combined weight of the firstand second poly(vinyl acetal) resins. In some embodiments, one of thefirst and second poly(vinyl acetal) resins can be present in thecomposition, layer, or interlayer in an amount in the range of fromabout 0.5 to about 12, about 1.5 to about 11.5, about 2 to about 11,about 2.5 to about 10 weight percent, based on the combined weight ofthe first and second poly(vinyl acetal) resins.

The first and second poly(vinyl acetal) resins can include residues ofany suitable aldehyde and, in some embodiments, can include residues ofat least one C₁ to C₁₀ aldehyde, at least one C₄ to C₈ aldehyde.Examples of suitable C₄ to C₈ aldehydes can include, but are not limitedto, n-butyraldehyde, iso-butyraldehyde, 2-methylvaleraldehyde, n-hexylaldehyde, 2-ethylhexyl aldehyde, n-octyl aldehyde, and combinationsthereof. At least one of the first and second poly(vinyl acetal) resinscan include at least about 20, at least about 30, at least about 40, atleast about 50, at least about 60, or at least about 70 weight percentof residues of at least one C₄ to C₈ aldehyde, based on the total weightof aldehyde residues of the resin, and/or can include not more thanabout 90, not more than about 85, not more than about 80, not more thanabout 75, not more than about 70, or not more than about 65 weightpercent of at least one C₄ to C₈ aldehyde, or in the range of from about20 to about 90, about 30 to about 80, or about 40 to about 70 weightpercent of at least one C₄ to C₈ aldehyde. The C₄ to C₈ aldehyde may beselected from the group listed above, or it can be selected from thegroup consisting of n-butyraldehyde, iso-butyraldehyde, 2-ethylhexylaldehyde, and combinations thereof.

In various embodiments, the first and/or second poly(vinyl acetal) resinmay be a polyvinyl n-butyral (PVB) resin. In other embodiments, thefirst and/or second poly(vinyl acetal) resin can be a poly(vinyln-butyral) resin that mainly comprises residues of n-butyraldehyde, andmay, for example, include not more than about 50, not more than about40, not more than about 30, not more than about 20, not more than about10, not more than about 5, or not more than about 2 weight percent ofresidues of an aldehyde other than n-butyraldehyde, based on the totalweight of all aldehyde residues of the resin. When the first and/orsecond poly(vinyl acetal) resins are PVB resins, the molecular weight ofthe resins can be at least about 50,000, at least about 70,000, at leastabout 100,000 Daltons and/or not more than about 600,000, not more thanabout 550,000, not more than about 500,000, not more than about 450,000,or not more than 425,000 Daltons, measured by size exclusionchromatography using low angle laser light scattering (SEC/LALLS) orUV/differential refractometer detectors. As used herein, the term“molecular weight” refers to weight average molecular weight (M_(w)).The molecular weight of the first and/or second poly(vinyl acetal) resincan be in the range of from about 50,000 to about 600,000, about 70,000to about 450,000, or about 100,000 to about 425,000 Daltons.

Although generally described herein with respect to first and secondpoly(vinyl acetal) resins, it should be understood that, in someembodiments, an equivalent single poly(vinyl acetal) resin includingfirst and second acetal moieties may be substituted for the first andsecond poly(vinyl acetal) resins with similar results. As used herein,the term “poly(vinyl acetal) resin component” can refer to an individualpoly(vinyl acetal) resin present in a blend of resins or to an acetalmoiety present on a single poly(vinyl acetal) resin. In variousembodiments, the ratio, by weight, of the amount of the first poly(vinylacetal) resin component to the second poly(vinyl acetal) resin componentin a layer, interlayer, or blend can be in the range of from about0.5:99.5 to about 99.5:0.5, about 1:99 to 99:1, about 10:90 to about90:10, about 25:75 to about 75:25, or about 40:60 to about 60:40.

In some embodiments, at least one resin composition, layer, orinterlayer can include at least a first poly(vinyl acetal) resincomponent and a second poly(vinyl acetal) resin component. In someembodiments, the first and second resin components may comprise firstand second poly(vinyl acetal) resins that can be physically mixed toform a resin blend, which may be combined with one or more plasticizersor other additives to provide a blended resin layer or interlayer. Inother embodiments, the first and second poly(vinyl acetal) resincomponents may be present as respective first and second acetal moietiesin a single poly(vinyl acetal) resin. As with the resin blend, thissingle “hybrid” poly(vinyl acetal) resin can be optionally blended witha plasticizer and utilized in resin layers and interlayers.

In some embodiments, when the resin components include poly(vinylacetal) resins, the first and second poly(vinyl acetal) resins may beblended such that one of the first and second resins is dispersed withinthe other of the first and second resins, which can form domains of oneof the first and second poly(vinyl acetal) resins within the other ofthe first and second poly(vinyl acetal) resins. Such a blended resin maybe used as a single layer interlayer or it may be combined with one ormore adjacent layers to form a multilayer interlayer. In otherembodiments, the first and second poly(vinyl acetal) resins can bepresent in adjacent layers of a multilayer interlayer, such that one ofthe layers of the interlayer includes the first poly(vinyl acetal) resinand another layer of the interlayer includes the second poly(vinylacetal) resin. Additional layers can also be present adjacent to atleast one of the layers.

The resin compositions, layers, and interlayers according to variousembodiments of the present invention can further include at least oneplasticizer. Depending on the specific composition of the resin orresins in a composition, layer, or interlayer, the plasticizer may bepresent in an amount of at least about 5, at least about 10, at leastabout 15, at least about 20, at least about 25, at least about 30, atleast about 35, at least about 40, at least about 45, at least about 50,at least about 55, at least about 60 parts per hundred parts of resin(phr) and/or not more than about 120, not more than about 110, not morethan about 105, not more than about 100, not more than about 95, notmore than about 90, not more than about 85, not more than about 75, notmore than about 70, not more than about 65, not more than about 60, notmore than about 55, not more than about 50, not more than about 45, ornot more than about 40 phr, or in the range of from about 5 to about120, about 10 to about 110, about 10 to about 100, about 20 to about 90,or about 25 to about 75 phr. Specific embodiments are discussed indetail shortly.

As used herein, the term “parts per hundred parts of resin” or “phr”refers to the amount of plasticizer present as compared to one hundredparts of resin, on a weight basis. For example, if 30 grams ofplasticizer were added to 100 grams of a resin, the plasticizer would bepresent in an amount of 30 phr. If the resin composition, layer, orinterlayer includes two or more resins, the weight of plasticizer iscompared to the combined amount of all resins present to determine theparts per hundred resin. Further, when the plasticizer content of alayer or interlayer is provided herein, it is provided with reference tothe amount of plasticizer in the mix or melt that was used to producethe layer or interlayer.

Examples of suitable plasticizers can include, but are not limited to,triethylene glycol di-(2-ethylhexanoate) (“3GEH”), triethylene glycoldi-(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethyleneglycol diheptanoate, tetraethylene glycol di-(2-ethylhexanoate)(“4GEH”), dihexyl adipate, dioctyl adipate, hexyl cyclohexyladipate,diisononyl adipate, heptylnonyl adipate, di(butoxyethyl) adipate, andbis(2-(2-butoxyethoxy)ethyl) adipate, dibutyl sebacate, dioctylsebacate, and mixtures thereof. The plasticizer may be selected from thegroup consisting of triethylene glycol di-(2-ethylhexanoate) andtetraethylene glycol di-(2-ethylhexanoate), or the plasticizer cancomprise triethylene glycol di-(2-ethylhexanoate).

According to some embodiments, the first and second poly(vinyl acetal)resins in the compositions, layers, and interlayers described herein canhave different compositions. For example, in some embodiments, the firstpoly(vinyl acetal) resin can have a residual hydroxyl content and/orresidual acetate content that is at least about 2, at least about 3, atleast about 4, at least about 5, at least about 6, or at least about 8weight percent higher or lower than the residual hydroxyl content and/orresidual acetate content of the second poly(vinyl acetal) resin. As usedherein, the terms “residual hydroxyl content” and “residual acetatecontent” refer to the amount of hydroxyl and acetate groups,respectively, that remain on a resin after processing is complete. Forexample, polyvinyl n-butyral can be produced by hydrolyzing polyvinylacetate to polyvinyl alcohol, and then acetalizing the polyvinyl alcoholwith n-butyraldehyde to form polyvinyl n-butyral. In the process ofhydrolyzing the polyvinyl acetate, not all of the acetate groups areconverted to hydroxyl groups, and residual acetate groups remain on theresin. Similarly, in the process of acetalizing the polyvinyl alcohol,not all of the hydroxyl groups are converted to acetal groups, whichalso leaves residual hydroxyl groups on the resin. As a result, mostpoly(vinyl acetal) resins include both residual hydroxyl groups (asvinyl hydroxyl groups) and residual acetate groups (as vinyl acetategroups) as part of the polymer chain. The residual hydroxyl content andresidual acetate content are expressed in weight percent, based on theweight of the polymer resin, and are measured according to ASTM D-1396,unless otherwise noted.

The difference between the residual hydroxyl content of the first andsecond poly(vinyl acetal) resins could also be at least about 2, atleast about 5, at least about 10, at least about 12, at least about 15,at least about 20, or at least about 30 weight percent. As used herein,the term “weight percent different” or “the difference is at leastweight percent” refers to a difference between two given weightpercentages, calculated by subtracting the one number from the other.For example, a poly(vinyl acetal) resin having a residual hydroxylcontent of 12 weight percent has a residual hydroxyl content that is 2weight percent lower than a poly(vinyl acetal) resin having a residualhydroxyl content of 14 weight percent (14 weight percent−12 weightpercent=2 weight percent). As used herein, the term “different” canrefer to a value that is higher than or lower than another value.

At least one of the first and second poly(vinyl acetal) resins can havea residual hydroxyl content of at least about 14, at least about 14.5,at least about 15, at least about 15.5, at least about 16, at leastabout 16.5, at least about 17, at least about 17.5, at least about 18,at least about 18.5, at least about 19, at least about 19.5 and/or notmore than about 45, not more than about 40, not more than about 35, notmore than about 33, not more than about 30, not more than about 27, notmore than about 25, not more than about 22, not more than about 21.5,not more than about 21, not more than about 20.5, or not more than about20 weight percent, or in the range of from about 14 to about 45, about16 to about 30, about 18 to about 25, about 18.5 to about 20, or about19.5 to about 21 weight percent.

The other poly(vinyl acetal) resin can have a residual hydroxyl contentof at least about 8, at least about 9, at least about 10, at least about11 weight percent and/or not more than about 16, not more than about 15,not more than about 14.5, not more than about 13, not more than about11.5, not more than about 11, not more than about 10.5, not more thanabout 10, not more than about 9.5, or not more than about 9 weightpercent, or in the range of from about 8 to about 16, about 9 to about15, or about 9.5 to about 14.5 weight percent, and can be selected suchthat the difference between the residual hydroxyl content of the firstand second poly(vinyl acetal) resin is at least about 2 weight percent,as mentioned previously. One or more other poly(vinyl acetal) resins mayalso be present in the resin composition, layer, or interlayer and canhave a residual hydroxyl within the ranges provided above. Additionally,the residual hydroxyl content of the one or more other poly(vinylacetal) resins can be the same as or different than the residualhydroxyl content of the first and/or second poly(vinyl acetal) resins.

In some embodiments, at least one of the first and second poly(vinylacetal) resins can have a residual acetate content different than theother. For example, in some embodiments, the difference between theresidual acetate content of the first and second poly(vinyl acetal)resins can be at least about 2, at least about 3, at least about 4, atleast about 5, at least about 8, at least about 10 weight percent. Oneof the poly(vinyl acetal) resins may have a residual acetate content ofnot more than about 4, not more than about 3, not more than about 2, ornot more than about 1 weight percent, measured as described above. Insome embodiments, at least one of the first and second poly(vinylacetal) resins can have a residual acetate content of at least about 5,at least about 8, at least about 10, at least about 12, at least about14, at least about 16, at least about 18, at least about 20, or at leastabout 30 weight percent. The difference in the residual acetate contentbetween the first and second poly(vinyl acetal) resins can be within theranges provided above, or the difference can be less than about 3, notmore than about 2, not more than about 1, or not more than about 0.5weight percent. Additional poly(vinyl acetal) resins present in theresin composition or interlayer can have a residual acetate content thesame as or different than the residual acetate content of the firstand/or second poly(vinyl acetal) resin.

In some embodiments, the difference between the residual hydroxylcontent of the first and second poly(vinyl acetal) resins can be lessthan about 2, not more than about 1, not more than about 0.5 weightpercent and the difference in the residual acetate content between thefirst and second poly(vinyl acetal) resins can be at least about 3, atleast about 5, at least about 8, at least about 15, at least about 20,or at least about 30 weight percent. In other embodiments, thedifference in the residual acetate content of the first and secondpoly(vinyl acetal) resins can be less than about 3, not more than about2, not more than about 1, or not more than about 0.5 weight percent andthe difference in the residual hydroxyl content of the first and secondpoly(vinyl acetal) resins can be at least about 2, at least about 5, atleast about 10, at least about 12, at least about 15, at least about 20,or at least about 30 weight percent.

In various embodiments, the differences in residual hydroxyl and/orresidual acetate content of the first and second poly(vinyl acetal)resins can be selected to control or provide certain performanceproperties, such as strength, impact resistance, penetration resistance,processability, or acoustic performance to the final composition, layer,or interlayer. For example, poly(vinyl acetal) resins having a higherresidual hydroxyl content, usually greater than about 16 weight percent,can facilitate high impact resistance, penetration resistance, andstrength to a resin composition or layer, while lower hydroxyl contentresins, usually having a residual hydroxyl content of less than 16weight percent, can improve the acoustic performance of the interlayeror blend.

Poly(vinyl acetal) resins having higher or lower residual hydroxylcontents and/or residual acetate contents may also, when combined withat least one plasticizer, ultimately include different amounts ofplasticizer. As a result, layers or domains formed of first and secondpoly(vinyl acetal) resins having different compositions may also havedifferent properties within a single resin layer or interlayer. Althoughnot wishing to be bound by theory, it is assumed that the compatibilityof a given plasticizer with a poly(vinyl acetal) resin can depend, atleast in part, on the composition of the polymer, and, in particular, onits residual hydroxyl content. Overall, poly(vinyl acetal) resins withhigher residual hydroxyl contents tend to exhibit a lower compatibility(or capacity) for a given plasticizer as compared to similar resinshaving a lower residual hydroxyl content. As a result, poly(vinylacetal) resins with higher residual hydroxyl contents tend to be lessplasticized and exhibit higher stiffness than similar resins havinglower residual hydroxyl contents. Conversely, poly(vinyl acetal) resinshaving lower residual hydroxyl contents may tend to, when plasticizedwith a given plasticizer, incorporate higher amounts of plasticizer,which may result in a softer resin layer that exhibits a lower glasstransition temperature than a similar resin having a higher residualhydroxyl content. Depending on the specific resin and plasticizer, thesetrends could be reversed.

When two poly(vinyl acetal) resins having different levels of residualhydroxyl content are blended with a plasticizer, the plasticizer maypartition between the resin layers or domains, such that moreplasticizer can be present in the layer or domain having the lowerresidual hydroxyl content and less plasticizer may be present in thelayer or domain having the higher residual hydroxyl content. Ultimately,a state of equilibrium is achieved between the two resins. Thecorrelation between the residual hydroxyl content of a poly(vinylacetal) resin and plasticizer compatibility/capacity can facilitateaddition of a proper amount of plasticizer to the polymer resin. Such acorrelation also helps to stably maintain the difference in plasticizercontent between two or more resins when the plasticizer would otherwisemigrate between the resins.

In some embodiments, a resin layer or interlayer can include at least afirst resin layer comprising a first poly(vinyl acetal) resin and afirst plasticizer, and a second resin layer, adjacent to the first resinlayer, comprising a second poly(vinyl acetal) resin and a secondplasticizer. The first and second plasticizer can be the same type ofplasticizer, or the first and second plasticizers may be different. Insome embodiments, at least one of the first and second plasticizers mayalso be a blend of two or more plasticizers, which can be the same as ordifferent than one or more other plasticizers. When one of the first andsecond poly(vinyl acetal) resins has a residual hydroxyl content that isat least 2 weight percent higher or lower than the residual hydroxylcontent of the other, the difference in plasticizer content between theresin layers can be at least about 2, at least about 5, at least about8, at least about 10, at least about 12, or at least about 15 phr. Inmost embodiments, the resin layer that includes the resin having a lowerhydroxyl content can have the higher plasticizer content. In order tocontrol or retain other properties of the resin layer or interlayer, thedifference in plasticizer content between the first and second resinlayers may be not more than about 40, not more than about 30, not morethan about 25, not more than about 20, or not more than about 17 phr. Inother embodiments, the difference in plasticizer content between thefirst and second resin layers can be at least about 40, at least about50, at least about 60, or at least about 70 phr.

As a result, in some embodiments, wherein the first and secondpoly(vinyl acetal) resins are present in adjacent layers of a multilayerinterlayer, the first and second resin layers can exhibit differentglass transition temperatures. Similarly, when the first and secondpoly(vinyl acetal) resins are present in a blend, the domains of one ofthe first and second poly(vinyl acetal) resins can exhibit a differentglass transition temperature than the other of the first and secondpoly(vinyl acetal) resins. Glass transition temperature, or T_(g), isthe temperature that marks the transition from the glass state of thepolymer to the rubbery state. The glass transition temperatures of theresins and layers described herein were determined by dynamic mechanicalthermal analysis (DMTA). The DMTA measures the storage (elastic) modulus(G′) in Pascals, loss (viscous) modulus (G″) in Pascals, and the tandelta (G″/G′) of the specimen as a function of temperature at a givenoscillation frequency and temperature sweep rate. The glass transitiontemperature is then determined by the position of the tan delta peak onthe temperature scale. Glass transition temperatures provided hereinwere determined at an oscillation frequency of 1 Hz under shear mode anda temperature sweep rate of 3° C./min.

The difference in the glass transition temperature of the first resinlayer and the second resin layer, or between various regions of ablended resin or resin layer, can be at least about 3, at least about 5,at least about 8, at least about 10, at least about 12, at least about15, at least about 18, at least about 20, at least about 22, or at leastabout 25° C. One of the first and second resin layers can have a glasstransition temperature of at least about 26, at least about 28, at leastabout 30, at least about 33, at least about 35° C. and/or not more thanabout 70, not more than about 65, not more than about 60, not more thanabout 55, not more than about 50° C., or in the range of from about 26to about 70, about 30 to about 60, about 35 to about 50° C. The other ofthe first and second poly(vinyl acetal) resins can have a glasstransition temperature of not more than 25, not more than about 20, notmore than about 15, not more than about 10, not more than about 5, notmore than about 0, not more than about −5, or not more than about −10°C.

When the first and second poly(vinyl acetal) resins are blended with oneanother such that domains of one resin are dispersed within the other,such differences in plasticizer content and/or glass transitiontemperature may also exist between domains of the first and secondresins. For example, in some embodiments, a resin layer or interlayermay include various domains of higher or lower plasticizer contentand/or domains having higher or lower glass transition temperatures, asdescribed previously. In some embodiments, at least a portion of theresin layer or interlayer can have a glass transition temperature of atleast about 26, at least about 28, at least about 30, at least about 33,at least about 35° C. and/or not more than about 70, not more than about65, not more than about 60, not more than about 55, not more than about50° C., or in the range of from about 26 to about 70, about 28 to about60, about 35 to about 50° C. and/or at least a portion of the resinlayer or interlayer can have a glass transition temperature of not morethan 25, not more than about 20, not more than about 15, not more thanabout 10, not more than about 5, not more than about 0° C., not morethan about −5° C., or not more than about −10° C.

One or more resin blends, layers, and interlayers described herein mayinclude various other additives to impart particular properties orfeatures to the interlayer. Such additives can include, but are notlimited to, dyes, pigments, stabilizers such as ultraviolet stabilizers,antioxidants, anti-blocking agents, flame retardants, IR absorbers orblockers such as indium tin oxide, antimony tin oxide, lanthanumhexaboride (LaB6) and cesium tungsten oxide, processing aides, flowenhancing additives, lubricants, impact modifiers, nucleating agents,thermal stabilizers, UV absorbers, dispersants, surfactants, chelatingagents, coupling agents, adhesives, primers, reinforcement additives,and fillers.

Additionally, various adhesion control agents (“ACAs”) can be used inthe interlayers of the present disclosure to control the adhesion of thesheet to glass. In various embodiments, the amount of ACAs present in aresin composition, layer, or interlayer can be at least about 0.003, atleast about 0.01, at least about 0.025 and/or not more than about 0.15,not more than about 0.10, or not more than about 0.04 phr, or in therange of from about 0.003 to about 0.15, about 0.01 to about 0.10, orabout 0.025 to about 0.04 phr. Suitable ACAs can include, but are notlimited to, sodium acetate, potassium acetate, magnesium bis(2-ethylbutyrate), magnesium bis(2-ethylhexanoate), and combinations thereof, aswell as the ACAs disclosed in U.S. Pat. No. 5,728,472.

Resins having different compositions and plasticized resin layers havingdifferent properties also tend to exhibit different refractive indices,which can reduce the optical quality of the resulting layer or blend.Although not wishing to be bound by theory, it is believed that suchdifferences in refractive index may cause light that passes through thedifferent resin layers or domains to be refracted in differentdirections, which may cause haze in the final product. At times, theabsolute value of the difference between the refractive index of thefirst poly(vinyl acetal) resin or layer and the refractive index of thesecond poly(vinyl acetal) resin or layer, measured according to ASTMD542 at a wavelength of 589 nm and 25° C., can exceed 0.010. As aresult, these compositions, layers, or interlayers can have a haze valuegreater than 5 percent and/or a mottle value greater than 3.

However, in various embodiments of the present invention, compositions,layers, and interlayers comprising a poly(vinyl acetal) resin mayfurther include at least one refractive index (RI) balancing agent foradjusting the refractive index of the composition, layer, or interlayer.In some embodiments, the composition, layer, or interlayer may includeat least a first poly(vinyl acetal) resin and a second poly(vinylacetal) resin along with at least one RI balancing agent. In otherembodiments, the composition, layer, or interlayer may include a singlepoly(vinyl acetal) resin along with at least one RI balancing agent. Asdiscussed above, the RI balancing agent can be any suitable agentpresent in a resin or a resin blend, layer, or interlayer, or portionthereof, that increases or reduces the refractive index of at least oneresin or layer, which may improve the optical properties of theinterlayer as compared to an identical interlayer formed without an RIbalancing agent. In some embodiments, the resin blend, layer, orinterlayer may have a haze value of at least 5 percent when formed inthe absence of the RI balancing agent.

The RI balancing agent can be in any suitable form and may be physicallyblended with one or more resins or it can be chemically bonded, orreacted, with at least one resin so that the RI balancing agent isincorporated into the polymer chain. Examples of RI balancing agents caninclude, but are not limited to, liquid RI additives, solid RIadditives, and residues of at least one aldehyde present in one or moreof the poly(vinyl acetal) resins. Various embodiments of RI balancingagents, as well as resin compositions, layers, and interlayers includingthe same, will now be discussed in detail below.

The RI balancing agent may be present in the resin, resin layer, orinterlayer in an amount sufficient to modify the refractive index ofpoly(vinyl acetal) resin, resin layer, or interlayer. The RI balancingagent may also be present in the composition, layer, or interlayer in anamount sufficient to modify the refractive index of at least one of thetwo poly(vinyl acetal) resins, thereby minimizing the difference betweenthe refractive indices of two poly(vinyl acetal) resin layers havingdifferent refractive indices. The RI balancing agent may also minimizethe difference between the refractive index of one or more poly(vinylacetal) resins and one or more plasticizers within a resin composition,layer, or interlayer. In some embodiments, the RI balancing agent may bepresent in an amount sufficient to reduce the absolute value of thedifference between the refractive index the first poly(vinyl acetal)resin layer and the refractive index of the second poly(vinyl acetal)resin layer to not more than 0.010, not more than about 0.009, not morethan about 0.008, not more than about 0.007, not more than about 0.006,not more than about 0.005, not more than about 0.004, or not more thanabout 0.003. When a multilayer interlayer includes two or more resinlayers, the RI balancing agent may be present in one or both layers andcan, in some embodiments, be present in one of the layers in a higheramount than in one or more of the other layers.

In some embodiments, the RI balancing agent can comprise one or moreresidues of an aldehyde having a refractive index of at least 1.421, asmeasured by ASTM D542 at a wavelength of 589 nm and a temperature of 25°C. The RI balancing aldehyde, which may also be referred to herein as a“high refractive index aldehyde” or “high RI aldehyde,” can have arefractive index of at least about 1.425, at least about 1.450, at leastabout 1.475, at least about 1.500, at least about 1.510, or at leastabout 1.515 and/or not more than about 1.675, not more than about 1.650,or not more than about 1.625, or in the range of from about 1.425 toabout 1.675, about 1.475 to about 1.650, or about 1.515 to about 1.625.The high RI aldehyde may be an aromatic aldehyde that includes at leastone aromatic ring or group. Examples of aromatic aldehydes can include,but are not limited to, C₇ to C₃₀ aromatic aldehydes, C₈ to C₂₅ aromaticaldehydes, or C₉ to C₂₀ aromatic aldehydes. Specific examples of high RIaldehydes that can be used as RI balancing agents in various embodimentsof the present invention are listed in Table 1, below.

TABLE 1 Exemplary High RI Aldehydes Aldehyde Refractive IndexHexylcinnamaldehyde 1.517 Benzaldeyde 1.545 Cinnamaldehyde 1.6204-Chlorobenzaldehyde 1.585 4-t-butylphenylacetaldehyde 1.5302-phenylpropionaldehyde 1.517 Hydrocinnamaldehyde 1.523

When the RI balancing agent includes residues of at least one high RIaldehyde, at least one of the first and second poly(vinyl acetal) resinscan include residues of at least one high RI aldehyde in an amount of atleast about 0.5, at least about 1, at least about 5, at least about 10,at least about 15, at least about 20, at least about 25, at least about30, at least about 35, at least about 40, at least about 45, at leastabout 50, at least about 55, at least about 60, at least about 65, atleast about 70, at least about 75, at least about 80, at least about 85,at least about 90, at least about 95 percent and/or not more than about99.5, not more than about 99, not more than about 97, not more thanabout 95, not more than about 90, not more than about 85, not more thanabout 80, not more than about 75, not more than about 70, not more thanabout 65, or not more than about 60 weight percent, based on the totalweight of aldehyde residues of the first or second poly(vinyl acetal)resin. At least one of the first and second poly(vinyl acetal) resinscan include residues of at least one high RI aldehyde in an amount inthe range of from about 0.5 to about 99.5, about 10 to about 90, about25 to about 75, or about 40 to about 60 weight percent, based on thetotal weight of aldehyde residues of the first or second poly(vinylacetal) resin.

The amount of high RI aldehyde residues can be determined using acombination of Fourier Transform Infrared Spectroscopy (FT-IR) and SizeExclusion Chromatography (SEC) with UV detection. In particular, FT-IRis used to measure residual hydroxyl content of the resin and SEC isused to determine the amount of high RI aldehyde residues, with theamount of any other aldehyde residues being determined by thedifference. The FT-IR analysis is performed using a Perkin ElmerSpectrum 100 FT-IR Spectrometer (commercially available from PerkinElmer, Waltham, Mass.) with an ATR sampling attachment. The analysis isperformed using 8 scans at a 4 cm-1 resolution. Prior to testing, acalibration is generated from several poly(vinyl n-butyral) samples ofvarying residual hydroxyl content which have been dried in a desiccatorwith silica overnight at room temperature to remove excess moisture. Thepeak maximum wave number of the hydroxyl stretching band is correlatedwith the molar vinyl alcohol content of each sample, which waspreviously determined by ASTM D1396, and the resulting linear curve fitis used to predict molar residual hydroxyl content the samples beinganalyzed. These values can be converted to weight percent by calculationafter determination of the composition of the poly(vinyl acetal) resinusing SEC analysis has been completed, as described below.

The SEC analysis is performed using a Waters 2695 Alliance pump andautosampler with a Waters 410 inline differential refractive indexdetector and a Waters 2998 PDA inline UV detector (commerciallyavailable from Waters Corporation, Milford, Mass.) with DionexChromeleon v. 6.8 data acquisition software with an extension pack(commercially available from Thermo Fischer Scientific, Sunnyvale,Calif.). The analysis is performed with a PL Gel Mixed C (5 micron)column and Mixed E (3 micron) columns with an injection volume of 50microliters at a flow rate of 1.0 mL/minute. Samples are prepared bydissolving between 0.03 and 0.09 grams of resin in 10-15 mL of solventsand then filtering each through a 0.22 micron PTFE filter. Calibrationsof the chromatograph are performed using polystyrene standards(commercially available as PSBR250K from American Polymer StandardCorporation, Mentor, Ohio).

In some embodiments, only one of the first and second poly(vinyl acetal)resins includes residues of the high RI aldehyde, while, in otherembodiments, both of the resins may include such residues. Therefractive index of a resin comprising residues of a high RI aldehydecan be at least about 1.492, at least about 1.495, at least about 1.500,at least about 1.505, at least about 1.510, or at least about 1.515.

In various embodiments, at least one of the first and second poly(vinylacetal) resins may also include residues of at least one aldehyde havinga refractive index of less than 1.421. Examples of these aldehydes caninclude, for example, aliphatic aldehydes such as the C₄ to C₈ aldehydesdiscussed above. The aldehydes having a refractive index of less than1.421 can be selected from the group consisting of n-butyraldehyde,iso-butyraldehyde, and 2-ethylhexyl aldehyde.

When these residues are present, the first and/or second poly(vinylacetal) resin can include at least about 10, at least about 15, at leastabout 20, at least about 25, at least about 30, at least about 35, atleast about 40, at least about 45, at least about 50, at least about 55,at least about 60, at least about 65, at least about 70, at least about75, at least about 80, at least about 85, at least about 90, at leastabout 95 percent and/or not more than about 99, not more than about 97,not more than about 95, not more than about 90, not more than about 85,not more than about 80, not more than about 75, not more than about 70,not more than about 65, or not more than about 60 weight percent, ofthese aldehydes, based on the total weight of aldehyde residues of thefirst or second poly(vinyl acetal) resin.

The amount of residues of an aldehyde having a refractive index of lessthan 1.421 are determined using the FT-IR/SEC method described above andthen by calculation according to the following formula: 100 weightpercent−weight percent residual hydroxyl (from FT-IR)−weight percent ofhigh RI aldehyde residues (from SEC)−weight percent residual acetate(from FT-IR)=weight percent of residues of aldehyde having refractiveindex less than 1.421. The first and/or second poly(vinyl acetal) resincan include residues of an aldehyde having a refractive index of lessthan 1.421 in an amount in the range of from about 10 to about 99, about25 to about 75, or about 40 to about 60 weight percent, based on thetotal weight of aldehyde residues of the first or second poly(vinylacetal) resin. The refractive index of one of these resins can be lessthan about 1.492, less than about 1.491, or less than about 1.490,measured as described previously.

According to some embodiments, one of the first and second poly(vinylacetal) resins primarily includes residues of a high RI aldehyde, whilethe other of the first and second poly(vinyl acetal) resins primarilyincludes residues of at least one aldehyde having a refractive index ofless than 1.421. As used herein, the term “primarily” means at least 75weight percent, so that a poly(vinyl acetal) resin primarily includingresidues of a specified aldehyde includes at least 75 weight percent ofresidues of the specified aldehyde, based on the total weight ofaldehyde residues of that resin. The poly(vinyl acetal) resin primarilyincluding residues of a high RI aldehyde can include not more than about25, not more than about 20, not more than about 15, not more than about10, not more than about 5, not more than about 2, or not more than about1 weight percent of residues of other aldehydes having a refractiveindex less than 1.421, based on the total weight of aldehyde residues ofthe resin.

Similarly, the other poly(vinyl acetal) resin, which can primarilyinclude residues of an aldehyde having a refractive index of less than1.421, may comprise not more than about 25, not more than about 20, notmore than about 15, not more than about 10, not more than about 5, notmore than about 2, or not more than about 1 weight percent of residuesof a high RI aldehyde, based on the total weight of aldehyde residues ofthe resin, and may include at least about 75, at least about 80, atleast about 85, at least about 90, at least about 95, at least about 97,or at least about 99 percent of residues of one or more aldehydes havinga refractive index less than 1.421. In some embodiments, the ratio ofthe resin primarily including residues of the high RI aldehyde to theother resin or resins in the composition can be at least about 1:99, atleast about 5:95, at least about 10:90, at least about 20:80, at leastabout 25:75, at least about 30:70, at least about 40:60 and/or not morethan about 99:1, not more than about 95:5, not more than about 90:10,not more than about 85:15, not more than about 75:25, not more thanabout 70:30, or not more than about 60:40, or in the range of from about1:99 to 99:1, about 10:90 to about 90:10, about 25:75 to 75:25, or about40:60 to 60:40.

In other embodiments, at least one of the first and second poly(vinylacetal) resins includes residues of a high RI aldehyde and at least onealdehyde having a refractive index of less than 1.421, thereby forming a“hybrid” resin that includes residues of both high and low RI aldehydes.According to these embodiments, the amounts of the high RI aldehyderesidues and the residues of aldehydes having a refractive index of lessthan 1.421, as well as the weight ratios of one to the other, in thehybrid resin can be within the same ranges provided above with respectto the resin blends. When the first or second poly(vinyl acetal) resinincludes residues of both high RI and lower RI aldehydes, the other ofthe two poly(vinyl acetal) resins may also include residues of at leastone high RI aldehyde. Alternatively, the other of the two resins mayinclude little or no high RI aldehyde residues, such that it includesless than about 10, less than about 5, less than about 2, or less thanabout 1 weight percent of residues of a high RI aldehyde, with thebalance being residues of an aldehyde having a refractive index of lessthan 1.421, including, for example, aldehydes selected from the groupconsisting of n-butyraldehyde, iso-butyraldehyde, 2-ethylhexyl aldehyde,and combinations thereof.

When the interlayer is a multilayer interlayer, it can include at leastone resin layer having at least a first poly(vinyl acetal) resin andanother resin layer comprising at least a second poly(vinyl acetal)resin, wherein the difference between the residual hydroxyl content ofthe first poly(vinyl acetal) resin and the second poly(vinyl acetal)resin is at least 2 weight percent. One or both of the poly(vinylacetal) resins can include residues of a high RI aldehyde and one of theresin layers may have a refractive index that is higher or lower thanthe other by at least about 0.002, at least about 0.003, at least about0.004 and/or not more than about 0.010, not more than about 0.009, notmore than about 0.008, or not more than about 0.007, or by an amount inthe range of from about 0.002 to about 0.010, about 0.003 to about0.009, or about 0.004 to about 0.007. In some embodiments when theinterlayer includes at least three resin layers, the innermost resinlayer can have the higher refractive index, while in other embodiments,the refractive index of one or both of the outer resin layers may behigher. In some embodiments, only one of the first and second poly(vinylacetal) resins may include residues of the high RI aldehyde. In otherembodiments, both of the poly(vinyl acetal) resins may include residuesof at least one high RI aldehyde, but the resins can still exhibit adifference in refractive index within the ranges provided above.

One or both of the poly(vinyl acetal) resins can include residues of atleast one high RI aldehyde. In some embodiments, when the poly(vinylacetal) resin including such residues has a residual hydroxyl content ofnot more than, for example, 15 weight percent, the resin layer includingsuch a resin may have a glass transition temperature of less than 20,not more than about 15, not more than about 10, not more than about 5,not more than about 0, not more than about −5, or not more than about−10° C. and a refractive index of at least about 1.465, at least about1.470, at least about 1.475, at least about 1.480, at least about 1.485,or at least about 1.490, each measured as described previously. Theplasticizer content of the layer, according to various embodiments, canbe at least about 50, at least about 55, at least about 60, at leastabout 65 phr and/or not more than about 120, not more than about 110,not more than about 90, not more than about 85, not more than about 80,or not more than about 75 phr, or in the range of from about 50 to about120, about 55 to about 110, about 60 to about 90, or about 65 to about75 phr.

When the resin having the residues of a high RI aldehyde in themultilayer interlayer discussed above has a residual hydroxyl contentgreater than, for example 16 weight percent, the resin layer includingthat resin may have a glass transition temperature of at least about 26,at least about 30, at least about 33, or at least about 35° C., and arefractive index of at least about 1.470, at least about 1.475, at leastabout 1.480, at least about 1.485, or at least about 1.490, eachmeasured as described previously. The plasticizer content of the layer,according to some embodiments, can be less than 50 phr, not more thanabout 45 phr, not more than about 40 phr, not more than about 30, notmore than about 20 phr.

According to various embodiments of the present invention, the RIbalancing agent can comprise a liquid RI balancing agent. As usedherein, the term “liquid RI balancing agent” refers to an RI balancingagent that is liquid at standard conditions of 25° C. and 1 atm. In someembodiments, the liquid RI balancing agent can be, for example, a highRI plasticizer. As used herein, the term “high RI plasticizer,” refersto a plasticizer having a refractive index of at least 1.460, measuredas described previously. The high RI plasticizers suitable for use as RIbalancing agents can have a refractive index of at least about 1.460, atleast about 1.470, at least about 1.480, at least about 1.490, at leastabout 1.500, at least about 1.510, at least about 1.520 and/or not morethan about 1.600, not more than about 1.575, or not more than about1.550, measured as discussed above. The refractive index of the high RIplasticizers may be in the range of from about 1.460 to about 1.600,about 1.470 to about 1.575, about 1.480 to about 1.550, about 1.490 toabout 1.525, and/or the refractive index of the high RI plasticizers maybe at least 1.460, at least 1.650, at least 1.700.

Examples of types or classes of high RI plasticizers can include, butare not limited to, polyadipates (RI of about 1.460 to about 1.485);epoxides such as epoxidized soybean oils (RI of about 1.460 to about1.480); phthalates and terephthalates (RI of about 1.480 to about1.540); benzoates and toluates (RI of about 1.480 to about 1.550); andother specialty plasticizers (RI of about 1.490 to about 1.520).

General examples of suitable high RI plasticizers can include, but arenot limited to dioctyl terephthalate, dioctyl isophthalate, dioctylphthalate, octyl benzoate, diisononyl terephthalate, diisononylisophthalate, diisononyl phthalate, isononyl benzoate, di-2-ethylhexylterephthalate, di-2-ethylhexyl isophthalate, di-2-ethylhexyl phthalate,2-ethylhexyl benzoate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethyl) isophthalate, bis-(ethoxyethyl) phthalate, ethoxyethylbenzoate, bis-(ethoxyethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl)isophthalate, bis-(ethoxyethoxyethyl) phthalate, ethoxyethoxyethylbenzoate, bis-(butoxyethoxyethyl) terephthalate, bis-(butoxyethoxyethyl)isophthalate, bis-(butoxyethoxyethyl) phthalate, butoxyethoxyethylbenzoate, bis-(butoxyethoxyethoxyethyl) terephthalate,bis-(butoxyethoxyethoxyethyl) isophthalate,bis-(butoxyethoxyethoxyethyl) phthalate, butoxyethoxyethoxyethylbenzoate, bis-(butoxyethyl) terephthalate, bis-(butoxyethyl)isophthalate, bis-(butoxyethyl) phthalate, butoxyethyl benzoate,bis-(methoxyethyl) terephthalate, bis-(methoxyethyl) isophthalate,bis-(methoxyethyl) phthalate, methoxyethyl benzoate,bis-(2-ethylhexyloxyethyl) terephthalate, bis-(2-ethylhexyloxyethyl)isophthalate, bis-(2-ethylhexyloxyethyl) phthalate, 2-ethylhexyloxyethylbenzoate, bis-(2-ethylhexyloxyethoxyethyl) terephthalate, bis-(2-ethylhexyloxyethoxyethyl) isophthalate, bis-(2-ethyl hexyloxyethoxyethyl)phthalate, 2-ethyl hexyloxyethoxyethyl benzoate,bis-(2-ethylhexyloxyethoxyethoxyethyl) terephthalate,bis-(2-ethylhexyloxyethoxyethoxyethyl) isophthalate, bis-(2-ethylhexyloxyethoxyethoxyethyl) phthalate, 2-ethyl hexyloxyethoxyethoxyethylbenzoate, bis-(dodecyl) terephthalate, bis-(dodecyl) isophthalate,bis-(dodecyl) phthalate, dodecyl benzoate, dipropylene glycol benzoatepelargonate, diethylene glycol benzoate, di-α-propylene glycol benzoate,di-β-propylene glycol benzoate, triethylene glycol benzoate caprylate,triethylene glycol benzoate caprate, diethylene glycol benzoatecaprylate, diethylene glycol benzoate caprate, tetraethylene glycolbenzoate caprylate, tetraethylene glycol benzoate caprate,1,4-cyclohexanedimethanol benzoate pelargonate, diethylene glycolbenzoate laurate, triethylene glycol benzoate laurate, tetraethyleneglycol benzoate laurate, bis-(n-hexyl) terephthalate, bis-(n-hexyl)isophthalate, bis-(n-hexyl) phthalate, n-hexyl benzoate, bis-(n-butyl)terephthalate, bis-(n-butyl) isophthalate, bis-(n-butyl) phthalate,n-butyl benzoate, bis-(iso-octyl) terephthalate, bis-(iso-octyl)isophthalate, bis-(iso-octyl) phthalate, iso-octyl benzoate,1,2-butanediol dibenzoate, 1,3-butanediol dibenzoate, 1,4-butanedioldibenzoate, di-α-propylene glycol di-o-toluate, tri-α-propylene glycoldi-o-toluate, tetra-α-propylene glycol di-o-toluate, di-β-propyleneglycol di-o-toluate, tri-β-propylene glycol di-o-toluate,tetra-β-propylene glycol di-o-toluate, diethylene glycol di-o-toluate,triethylene glycol di-o-toluate, tetraethylene glycol di-o-toluate,2-butyl-2-ethyl-1,3-propanediol dibenzoate, 3-methyl-1,5-pentanedioldibenzoate, diethylene glycol di-p-toluate, triethylene glycoldi-p-toluate, tetraethylene glycol di-p-toluate, diethylene glycoldi-m-toluate, triethylene glycol di-m-toluate, tetraethylene glycoldi-m-toluate, di-α-propylene glycol di-p-toluate, tri-α-propylene glycoldi-p-toluate, tetra-α-propylene glycol di-p-toluate, di-β-propyleneglycol di-m-toluate, tri-β-propylene glycol di-m-toluate,tetra-β-propylene glycol di-m-toluate, di-α-propylene glycoldi-p-toluate, tri-α-propylene glycol di-p-toluate, tetra-α-propyleneglycol di-p-toluate, di-β-propylene glycol di-m-toluate, tri-β-propyleneglycol di-m-toluate, tetra-β-propylene glycol di-m-toluate, triethyleneglycol benzoate acetate, trioctyl trimellitate, and/or combinationsthereof.

Specific examples of suitable high RI plasticizers can include, but arenot limited to, dipropylene glycol dibenzoate, tripropylene glycoldibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate,2-ethylhexyl benzoate, diethylene glycol benzoate, butoxyethyl benzoate,butoxyethyoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, propyleneglycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, diethylene glycol di-o-toluate, triethylene glycoldi-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate,tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenolA bis(2-ethylhexaonate), di-(butoxyethyl) terephthalate,di-(butoxyethyoxyethyl) terephthalate, and mixtures thereof. The high RIplasticizer may be selected from dipropylene glycol dibenzoate andtripropylene glycol dibenzoate, and/or 2,2,4-trimethyl-1,3-pentanedioldibenzoate, trioctyl trimellitate, and/or combinations thereof.

In one embodiment, the high RI plasticizer comprises bis-(methoxyethyl)terephthalate, bis-(butoxyethyl) terephthalate, bis-(butoxyethoxyethyl)terephthalate, bis-(ethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl)terephthalate, bis-(2-ethylhexyloxyethyl) terephthalate,bis-(2-ethylhexyl) iso-phthalate, bis-(2-ethylhexyloxyethoxyethyl)terephthalate, 2-ethylhexyloxyethyl benzoate,2-ethylhexyloxyethoxylethyl benzoate, ethoxyethoxyethyl benzoate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, dodecylbenzoate, dipropylene glycol di-o-toluate, triethylene glycol benzoateacetate, trioctyl trimellitate, or combinations thereof.

In another embodiment, the high RI plasticizer comprisesbis-(methoxyethyl) terephthalate, bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(2-ethylhexyloxyethoxyethyl)terephthalate, 2-ethylhexyloxyethoxylethyl benzoate, ethoxyethoxyethylbenzoate, butoxyethoxyethoxyethyl benzoate, dipropylene glycoldi-o-toluate and triethylene glycol benzoate acetate, trioctyltrimellitate, or combinations thereof.

In another embodiment, the high RI plasticizer comprisesbis-(methoxyethyl) terephthalate, bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, ethoxyethoxyethyl benzoate,dipropylene glycol di-o-toluate, and triethylene glycol benzoateacetate, trioctyl trimellitate, or combinations thereof.

In another embodiment, the high RI plasticizer comprises dioctylphthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate,bis-(methoxyethyl) terephthalate, bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(2-ethylhexyloxyethyl)terephthalate, bis-(2-ethylhexyl) iso-phthalate,bis-(2-ethylhexyloxyethoxyethyl) terephthalate, 2-ethylhexyloxyethylbenzoate, 2-ethyl hexyloxyethoxylethyl benzoate, ethoxyethoxyethylbenzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate,dodecyl benzoate, dipropylene glycol di-o-toluate, triethylene glycolbenzoate acetate, trioctyl trimellitate, or combinations thereof.

In another embodiment, the high RI plasticizer comprisesbis-(methoxyethyl) terephthalate, bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(2-ethylhexyloxyethyl)terephthalate, bis-(2-ethylhexyl) iso-phthalate, ethoxyethoxyethylbenzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate,dodecyl benzoate, dipropylene glycol di-o-toluate, triethylene glycolbenzoate acetate, trioctyl trimellitate, or combinations thereof.

In another embodiment, the high RI plasticizer comprisesbis-(butoxyethyl) terephthalate, bis-(butoxyethoxyethyl) terephthalate,bis-(ethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl) terephthalate,bis-(2-ethylhexyl) iso-phthalate, butoxyethoxyethyl benzoate,butoxyethoxyethoxyethyl benzoate, dodecyl benzoate, dipropylene glycoldi-o-toluate, triethylene glycol benzoate acetate, trioctyltrimellitate, or combinations thereof.

In another embodiment, the plasticizer comprises a terephthalatecomprising one of the following compounds: dioctyl terephthalate,diisononyl terephthalate, bis-(2-ethylhexyloxyethyl) terephthalate,bis-(2-ethylhexyl) terephthalate, bis-(2-ethylhexyloxyethoxyethyl)terephthalate, bis-(2-ethyl hexyloxyethoxyethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(dodecyl) terephthalate,bis-(n-hexyl) terephthalate, bis-(n-butyl) terephthalate,bis-(iso-octyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(butoxyethoxyethyl)terephthalate, bis-(butoxyethoxyethoxyethyl) terephthalate,bis-(butoxyethyl) terephthalate, bis-(methoxyethyl) terephthalate, orcombinations thereof.

In another embodiment, the high RI plasticizer comprises an isophthalatecomprising one of the following compounds: dioctyl isophthalate,diisononyl isophthalate, di-2-ethylhexyl isophthalate, bis-(ethoxyethyl)isophthalate, bis-(ethoxyethoxyethyl) isophthalate,bis-(butoxyethoxyethyl) isophthalate, bis-(butoxyethoxyethoxyethyl)isophthalate, bis-(butoxyethyl) isophthalate, bis-(methoxyethyl)isophthalate, bis-(2-ethylhexyloxyethyl) isophthalate, bis-(2-ethylhexyloxyethoxyethyl) isophthalate,bis-(2-ethylhexyloxyethoxyethoxyethyl) isophthalate,bis-(ethoxyethoxyethyl) isophthalate, bis-(dodecyl) isophthalate,bis-(n-hexyl) isophthalate, bis-(n-butyl) isophthalate, bis-(iso-octyl)isophthalate, bis-(2-ethylhexyl) isophthalate, or combinations thereof.

In another embodiment, the high RI plasticizer comprises a phthalatecomprising one of the following compounds: dioctyl phthalate, diisononylphthalate, bis-(ethoxyethyl) phthalate, bis-(ethoxyethoxyethyl)phthalate, bis-(butoxyethoxyethyl) phthalate,bis-(butoxyethoxyethoxyethyl) phthalate, bis-(butoxyethyl) phthalate,bis-(methoxyethyl) phthalate, bis-(2-ethylhexyloxyethyl) phthalate,bis-(2-ethylhexyl) phthalate, bis-(2-ethylhexyloxyethoxyethyl)phthalate, bis-(2-ethylhexyloxyethoxyethoxyethyl) phthalate,bis-(ethoxyethoxyethyl) phthalate, bis-(dodecyl) phthalate,bis-(n-hexyl) phthalate, bis-(n-butyl) phthalate, bis-(iso-octyl)phthalate, or combinations thereof.

In another embodiment, the high RI plasticizer comprises a benzoatecomprising one of the following compounds: octyl benzoate, isononylbenzoate, ethoxyethoxyethyl benzoate, butoxyethyl benzoate, methoxyethylbenzoate, 2-ethylhexyl benzoate, 2-ethyl hexyloxyethoxyethoxyethylbenzoate, ethoxyethoxyethyl benzoate, diethylene glycol benzoate,di-α-propylene glycol benzoate, di-β-propylene glycol benzoate, n-hexylbenzoate, n-butyl benzoate, iso-octyl benzoate, ethoxyethyl benzoate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, orcombinations thereof

In another embodiment, the high RI plasticizer comprises a toluatecomprising one of the following compounds: di-α-propylene glycoldi-o-toluate, tri-α-propylene glycol di-o-toluate, tetra-α-propyleneglycol di-o-toluate, di-β-propylene glycol di-o-toluate, tri-β-propyleneglycol di-o-toluate, tetra-β-propylene glycol di-o-toluate, triethyleneglycol di-o-toluate, tetraethylene glycol di-o-toluate, diethyleneglycol di-p-toluate, tetraethylene glycol di-p-toluate, diethyleneglycol di-m-toluate, triethylene glycol di-m-toluate, tetraethyleneglycol di-m-toluate, di-α-propylene glycol di-p-toluate, tri-α-propyleneglycol di-p-toluate, tetra-α-propylene glycol di-p-toluate,di-β-propylene glycol di-m-toluate, tri-β-propylene glycol di-m-toluate,tetra-(3-propylene glycol di-m-toluate, di-α-propylene glycoldi-p-toluate, tri-α-propylene glycol di-p-toluate, tetra-α-propyleneglycol di-p-toluate, di-β-propylene glycol di-m-toluate, tri-β-propyleneglycol di-m-toluate, tetra-β-propylene glycol di-m-toluate, diethyleneglycol di-o-toluate, triethylene glycol di-p-toluate, or combinationsthereof.

In another embodiment, the high RI plasticizer comprises a mixedbenzoate comprising one of the following compounds: dipropylene glycolbenzoate pelargonate, triethylene glycol benzoate caprylate, triethyleneglycol benzoate caprate, diethylene glycol benzoate caprylate,diethylene glycol benzoate caprate, tetraethylene glycol benzoatecaprylate, tetraethylene glycol benzoate caprate,1,4-cyclohexanedimethanol benzoate pelargonate, diethylene glycolbenzoate laurate, triethylene glycol benzoate laurate, tetraethyleneglycol benzoate laurate, triethylene glycol benzoate acetate, orcombinations thereof.

In another embodiment, the high RI plasticizer comprises at least one offollowing: (i) a terephthalate comprising one of the followingcompounds: bis-(2-ethyl hexyloxyethoxyethoxyethyl) terephthalate,bis-(2-ethyl hexyloxyethoxyethyl) terephthalate,bis-(2-ethylhexyloxyethyl) terephthalate, bis-(dodecyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(ethoxyethoxyethoxyethyl)terephthalate, bis-(butoxyethoxyethoxyethyl) terephthalate, orcombinations thereof; (ii) an isophthalate comprising one of thefollowing compounds: bis-(2-ethylhexyloxyethoxyethoxyethyl)isophthalate, bis-(2-ethylhexyloxyethoxyethyl) isophthalate,bis-(2-ethylhexyloxyethyl) isophthalate, bis-(butoxyethoxyethyl)isophthalate, bis-(butoxyethyl) isophthalate, bis-(dodecyl)isophthalate, bis-(ethoxyethoxyethyl) isophthalate.bis-(ethoxyethoxyethyl) isophthalate, bis-(ethoxyethyl) isophthalate,bis-(2-ethylhexyloxyethoxyethoxyethyl) isophthalate,bis-(ethoxyethoxyethoxyethyl) isophthalate,bis-(butoxyethoxyethoxyethyl) isophthalate, or combinations thereof;(iii) a phthalate comprising one of the following compounds:bis-(2-ethyl hexyloxyethoxyethoxyethyl) phthalate, bis-(2-ethylhexyloxyethoxyethyl) phthalate, bis-(2-ethylhexyloxyethyl) phthalate,bis-(2-ethylhexyloxyethoxyethoxyethyl) phthalate,bis-(ethoxyethoxyethoxyethyl) phthalate, bis-(butoxyethoxyethoxyethyl)phthalate, or combinations thereof; (iv) a benzoate comprising thefollowing compound: 2-ethylhexyloxyethoxyethoxyethyl benzoate; (v) atoluate comprising one of the following compounds: diethylene glycoldi-m-toluate, diethylene glycol di-p-toluate, di-α-propylene glycoldi-o-toluate, di-α-propylene glycol di-p-toluate, di-α-propylene glycoldi-p-toluate, di-β-propylene glycol di-m-toluate, di-β-propylene glycoldi-m-toluate, di-β-propylene glycol di-o-toluate, tetraethylene glycoldi-m-toluate, tetraethylene glycol di-o-toluate, tetraethylene glycoldi-p-toluate, tetra-α-propylene glycol di-o-toluate, tetra-α-propyleneglycol di-p-toluate, tetra-α-propylene glycol di-p-toluate,tetra-β-propylene glycol di-m-toluate, tetra-β-propylene glycoldi-m-toluate, tetra-β-propylene glycol di-o-toluate, triethylene glycoldi-m-toluate, triethylene glycol di-o-toluate, tri-α-propylene glycoldi-o-toluate, tri-α-propylene glycol di-p-toluate, tri-α-propyleneglycol di-p-toluate, tri-β-propylene glycol di-m-toluate,tri-β-propylene glycol di-m-toluate, tri-p-propylene glycoldi-o-toluate, or combinations thereof; and/or (vi) a mixed benzoatecomprising one of the following compounds: 1,4-cyclohexanedimethanoldibenzoate, 1,4-cyclohexanedimethanol benzoate pelargonate,1,4-cyclohexanedimethanol benzoate laurate, 1,4-cyclohexanedimethanolbenzoate caprate, 1,4-cyclohexanedimethanol benzoate caprylate,3-methyl-1,5-pentanediol dibenzoate, diethyleneglycol benzoate caprate,diethyleneglycol benzoate caprylate, diethyleneglycol benzoate laurate,dipropyleneglycol benzoate pelargonate, tetraethyleneglycol benzoatecaprate, tetraethyleneglycol benzoate caprylate, tetraethyleneglycolbenzoate laurate, triethyleneglycol benzoate laurate, or combinationsthereof.

In another embodiment, the high RI plasticizer comprises at least one offollowing compounds:

or a combination thereof; wherein R is selected from the groupconsisting of hydrogen and a methyl group; wherein R′ is selected fromthe group consisting of hydrogen and an alkyl group having from 1 to 12carbon atoms; and wherein n is at least 3.

In another embodiment, R is a hydrogen, R is a methyl group, R is anethyl group, R is a propyl group, and/or R is an alkyl group having 1 to5 carbon atoms. In another embodiment, R′ comprises a methyl, ethyl,propyl, n-butyl, sec-butyl, pentyl, n-hexyl, 2-ethyl hexyl, heptyl,octyl group, or a combination therein. In another embodiment, n is atleast 3, n is at least 4, n is at least 5, n is at least 7, n is atleast 3 but less than 10, n is at least 3 but less than 9, n is at least3 but less than 8, n is at least 3 but less than 7, n is at least 3 butless than 6, n is at least 3 but less than 5, n is at least 4 but lessthan 10, n is at least 4 but less than 9, n is at least 4 but less than8, n is at least 4 but less than 7, and/or n is at least 4 but less than6.

In another embodiment, the high RI plasticizer comprises at least one ofthe following compounds: bis-(2-ethylhexyloxyethoxyethoxyethyl)terephthalate, bis-(ethoxyethoxyethoxyethyl) terephthalate,bis-(butoxyethoxyethoxyethyl) terephthalate,bis-(2-ethylhexyloxyethoxyethoxyethyl) isophthalate,bis-(ethoxyethoxyethoxyethyl) isophthalate,bis-(butoxyethoxyethoxyethyl) isophthalate,bis-(2-ethylhexyloxyethoxyethoxyethyl) phthalate,bis-(ethoxyethoxyethoxyethyl) phthalate, bis-(butoxyethoxyethoxyethyl)phthalate, or combinations thereof.

When the resin layer or interlayer includes a high RI plasticizer, theplasticizer can be present in the layer alone or it can be blended withone or more additional plasticizers. The other plasticizer orplasticizers may also comprise high RI plasticizers, or one or more maybe a lower RI plasticizer having a refractive index of less than 1.460.In some embodiments, the lower RI plasticizer may have a refractiveindex of less than about 1.450, less than about 1.445, or less thanabout 1.442 and can be selected from the group listed previously. When amixture of two or more plasticizers are employed as a RI balancingagent, the mixture can have a refractive index within one or more of theabove ranges.

When used as an RI balancing agent in a multilayer interlayer, a high RIplasticizer may be present in different amounts in two or more of theresin layers. Similarly, when used as an RI balancing agent in a resincomposition or blended resin layer, the high RI plasticizer may bepartitioned as described previously, such that resin layers or domainshaving a lower residual hydroxyl content may have higher amounts of thehigh RI plasticizer. In some embodiments, at least one layer or portionof a resin layer or interlayer may comprise a high RI plasticizer as anRI balancing agent in an amount of at least about 5, at least about 10,at least about 15, at least about 20, at least about 25, at least about30, at least about 35 and/or not more than about 50, not more than about45, or not more than about 40 phr. The high RI plasticizer can bepresent in the resin layer or interlayer in an amount in the range offrom about 5 to about 50, about 10 to about 45, about 20 to about 40phr. In some embodiments, one or more other layers or portions caninclude the high RI plasticizer in an amount of at least about 50, atleast about 55, at least about 60, at least about 65, at least about 70and/or not more than about 120, not more than about 110, not more thanabout 100, not more than about 90, or not more than about 75 phr, or inthe range of from about 50 to about 120, about 55 to about 110, about 60to about 90, about 65 to about 75 phr. These amounts may include anyother plasticizers present in the composition, including those having arefractive index less than 1.460, or may include only the high RIplasticizer.

When a high RI plasticizer is used as an RI balancing agent in amultilayer interlayer, the interlayer can include at least one resinlayer having a first poly(vinyl acetal) resin and another resin layercomprising a second poly(vinyl acetal) resin, wherein the differencebetween the residual hydroxyl content of the first poly(vinyl acetal)resin and the second poly(vinyl acetal) resin is at least 2 weightpercent. At least one of the resin layers can include a high RIplasticizer in an amount sufficient so that the absolute value of thedifference between the refractive index of the resin layer and therefractive index of the another resin layer is not more than 0.010. Insome embodiments when the interlayer includes at least three resinlayers, the innermost resin layer can have a higher refractive index,while in other embodiments, the refractive index of one or both of theouter resin layers may be higher.

In another embodiment, a high RI plasticizer can be used as an RIbalancing agent in a multilayer interlayer, the interlayer can includeat least one resin layer having a first poly(vinyl acetal) resin andanother resin layer comprising a second poly(vinyl acetal) resin,wherein the difference between the residual hydroxyl content of thefirst poly(vinyl acetal) resin and the second poly(vinyl acetal) resinis at least 2 weight percent or at least 1 weight percent. At least oneof the resin layers can include a high RI plasticizer in an amountsufficient so that the absolute value of the difference between therefractive index of the resin layer and the refractive index of theanother resin layer is not more than 0.010. In some embodiments, theinterlayer can include at least one resin layer having a firstpoly(vinyl acetal) resin and a first high RI plasticizer and anotherresin layer comprising a second poly(vinyl acetal) resin and a secondhigh RI plasticizer, wherein the first high RI plasticizer and thesecond high RI plasticizer may be the same or different plasticizers. Insome embodiments, the first poly(vinyl acetal) resin and a secondpoly(vinyl acetal) resin may have the same residual hydroxyl content butmay vary in their molecular weight and/or residual acetate content. Insome embodiments when the interlayer includes at least three resinlayers, the innermost resin layer can have a higher refractive index,while in other embodiments, the refractive index of one or both of theouter resin layers may be higher.

When a high RI plasticizer is included in a resin layer that includes atleast one poly(vinyl acetal) resin having the lower residual hydroxylcontent, at least a portion of the resin layer can have a glasstransition temperature of not more than 25, not more than about 20, notmore than about 15, not more than about 10, not more than about 5, notmore than about 0, not more than about −5, or not more than about −10°C., and the layer can have a refractive index of at least about 1.465,at least about 1.470, at least about 1.475, at least about 1.480, atleast about 1.485, or at least about 1.490, at least about 1.495measured as described previously. The plasticizer content of this layer,in some embodiments, can be at least about 50, at least about 55, atleast about 60 phr and/or not more than about 120, not more than about110, not more than about 90, not more than about 85, not more than about80, or not more than about 75 phr, or in the range of from about 50 toabout 120, about 55 to about 110, about 60 to about 90, or about 60 toabout 75 phr.

When the high RI plasticizer is present in the resin layer thatcomprises the poly(vinyl acetal) resin having a higher residual hydroxylcontent, at least a portion of the layer can have a glass transitiontemperature of at least about 26, at least about 30, at least about 33,or at least about 35° C., and the layer can have a refractive index ofat least about 1.470, at least about 1.475, at least about 1.480, atleast about 1.485, or at least about 1.490, measured as describedpreviously. The plasticizer content of this layer, according to someembodiments, can be less than 50 phr, not more than about 45 phr, notmore than about 40 phr, not more than about 30, or not more than about20 phr.

According to various embodiments of the present invention, the RIbalancing agent may be a solid RI additive present in one or more layersor portions of a layer or interlayer. As used herein, the term “solid RIadditive” refers to an additive used to adjust the refractive index of apoly(vinyl acetal) resin, resin layer, or interlayer and which is solidat ambient conditions of 25° C. and 1 atm. In various embodiments, thesolid RI additive may have a melting point of at least about 27, atleast about 30, at least about 35, at least about 40, at least about 45,at least about 50, at least about 55, at least about 60, at least about75, at least about 80, at least about 85, at least about 90, at leastabout 95, or at least about 100° C. When employed in a resin blend,layer, or interlayer, the solid RI additive can be present in an amountsufficient such that the absolute value of the difference between therefractive indices of the first and second resin layers is not more thanabout 0.010. The difference between the refractive index of the firstand second resin layers may be greater than 0.010, when formulated intoidentical resin layers in the absence of the solid RI additive.

In some embodiments, the solid RI additive can be a high RI solidadditive for increasing the refractive index of at least one resin layeror interlayer. The refractive index of the high RI solid additive can beat least about 1.460, at least about 1.465, at least about 1.470, atleast about 1.475, at least about 1.480, at least about 1.485, at leastabout 1.490, at least about 1.495, at least about 1.500, at least about1.505, at least about 1.510, at least about 1.525, at least about 1.550,at least about 1.575, or at least about 1.600, measured as describedpreviously. In other embodiments, the solid RI additive may be a RIlowering solid additive for reducing the refractive index of at leastone resin or resin layer. The RI lowering solid additive can have arefractive index of less than 1.460, not more than about 1.455, not morethan about 1.450, not more than about 1.445, or not more than about1.440, measured as described previously. Whether higher or lower, thesolid RI additive can have a refractive index that is at least about0.005, at least about 0.010, at least about 0.050, at least about 0.10and/or not more than about 0.50, not more than about 0.35, or not morethan about 0.20 different than the refractive index of the poly(vinylacetal) resin. The difference in refractive index between the solid RIadditive and the poly(vinyl acetal) resin can be in the range of fromabout 0.005 to about 0.50, about 0.010 to about 0.35, or about 0.050 toabout 0.35.

In various embodiments, the solid RI additive can be present in a resincomposition or interlayer in an amount of at least about 0.5, at leastabout 1, at least about 1.5, at least about 2, or at least about 5 phr,depending on the specific type of additive and layer or interlayer. Thesolid RI additive, whether a high RI additive or an RI loweringadditive, may comprise a physical solid RI additive capable of beingphysically mixed or blended with at least one poly(vinyl acetal) resinin a resin composition or layer, or it can be a reactive solid RIadditive, which may react with and become incorporated into the backboneof one or more poly(vinyl acetal) resins.

The solid RI additive can be used in combination with one or more low RIplasticizers. Examples of low RI plasticizers can include, but are notlimited to, triethylene glycol di-(2-ethylhexanoate) (“3GEH”),triethylene glycol di-(2-ethylbutyrate), triethylene glycoldiheptanoate, tetraethylene glycol diheptanoate, tetraethylene glycoldi-(2-ethylhexanoate) (“4GEH”), dihexyl adipate, dioctyl adipate, hexylcyclohexyladipate, diisononyl adipate, heptylnonyl adipate,di(butoxyethyl) adipate, and bis(2-(2-butoxyethoxy)ethyl) adipate,dibutyl sebacate, dioctyl sebacate, and mixtures thereof. Theplasticizer may be selected from the group consisting of triethyleneglycol di-(2-ethylhexanoate) and tetraethylene glycoldi-(2-ethylhexanoate), or the plasticizer can comprise triethyleneglycol di-(2-ethylhexanoate). The solid RI additive can also be used incombination with one or more high RI plasticizers mentioned previously.

When the solid RI additive is a physical solid RI additive, it may becombined with one or more poly(vinyl acetal) resins or layers in aninterlayer. In some embodiments, the physical solid RI additive may bepresent in at least one layer or in an interlayer in an amount of atleast about 1, at least about 2, at least about 3, at least about 5, atleast about 8, at least about 10, at least about 12, at least about 15,at least about 20 and/or not more than about 60, not more than about 55,not more than about 50, not more than about 45, not more than about 40,not more than about 35, not more than about 30, not more than about 25,not more than about 20, or not more than about 15 phr, or in an amountin the range of from about 1 to about 60, about 5 to about 50, or about10 to about 45 phr. Examples of suitable physical solid high RIadditives can include, but are not limited to, polyadipates, polystyrenehaving a molecular weight of less than 2500, epoxides, phthalic acidesters, benzoic acid esters, inorganic oxides such as, for example,zirconium oxide, and combinations thereof. Physical solid RI loweringadditives can be selected from the group consisting of halogenatedadditives, and silicon-containing additives.

When utilized in a multilayer interlayer, the physical solid RI additivemay be present in one of the resin layers in a higher amount than one ormore other layers. The difference between the amount of the physicalsolid RI additive present in one of the resin layers and the amount ofphysical solid RI additive present in another layer, including, forexample, an adjacent layer, can be at least about 2, at least about 5,at least about 8, at least about 10 phr and/or not more than about 30,not more than about 25, or not more than about 20 phr, or it can be inthe range of from about 2 to about 30, about 5 to about 25, or about 10to about 20 phr. According to some embodiments, at least one of thelayers can include at least about 1, at least about 5, at least about10, at least about 15 phr and/or not more than about 60, not more thanabout 55, not more than about 50, not more than about 45 phr of thephysical solid RI additive, or the physical solid RI additive can bepresent in an amount in the range of from about 1 to about 60, about 10to about 50, or about 15 to about 45 phr. In some embodiments, thephysical solid RI additive can be present in one or more layers in anamount of at least about 5, at least about 10, at least about 15, atleast about 20 phr and/or not more than about 60, not more than about55, not more than about 50 phr, or in an amount in the range of fromabout 5 to about 60, about 15 to about 55, or about 20 to about 50 phr.

When the multilayer interlayer comprises three or more resin layers andthe solid RI additive is a solid high RI additive, the inner, or core,layer or layers can include higher amounts of the physical solid RIadditive than the outer, or skin, layers. However, if the solid RIadditive is a solid RI lowering additive, the outer skin layers mayinclude higher amounts of the solid RI additive than the inner corelayer. The core layer can include at least about 30, at least about 40,at least about 50, at least about 60, at least about 70, or at leastabout 80 percent of the total amount of physical solid RI additivepresent in the interlayer.

When the solid RI additive is a reactive solid RI additive, it may bereacted with at least one poly(vinyl acetal) resin such that at least aportion of the additive is incorporated into the polymer chain. Thereactive RI additive can be an aromatic additive and can comprise, insome embodiments, phthalic anhydrides and phenylalkoxysilanes including,for example, diphenyldimethoxysilane.

In some embodiments, the reactive RI additive may be present in onelayer of a multilayer interlayer in a higher amount than it is presentin one or more other layers of the interlayer. In some embodiments, itmay be absent, or substantially absent, from one or more resin layers.For example, when the interlayer is a multilayer interlayer including atleast three resin layers, the inner core layer may include at leastabout 0.5, at least about 1, at least about 1.5, at least about 2, atleast about 2.5, at least about 3 and/or not more than about 50, notmore than about 30, not more than about 20, not more than about 15, notmore than about 12, not more than about 10, or not more than about 8 phrof one or more reactive solid RI additives, or an amount in the range offrom about 0.5 to about 20, about 1 to about 12, or about 2 to about 8phr. The outer skin layer or layers may include not more than about 10,not more than about 5, not more than about 2, not more than about 1, ornot more than about 0.5 phr of the reactive solid RI additive. The corelayer can include at least about 65, at least about 75, at least about85, at least about 95, or at least about 99 percent of the total amountof the reactive RI additive present in the interlayer.

When a solid RI additive is used as an RI balancing agent in amultilayer interlayer, the interlayer can include at least one resinlayer having a first poly(vinyl acetal) resin and another resin layercomprising a second poly(vinyl acetal) resin, wherein the differencebetween the residual hydroxyl content of the first poly(vinyl acetal)resin and the second poly(vinyl acetal) resin is at least 2 weightpercent. At least one of the resin layers can include the high RIadditive in an amount sufficient so that the absolute value of thedifference between the refractive index of the first resin layer and therefractive index of the second resin layer is not more than 0.010. Insome embodiments when the interlayer includes at least three resinlayers, the innermost resin layer can have a higher refractive index,while in other embodiments, the refractive index of one or both of theouter resin layers may be higher.

When a solid RI additive is included in a resin layer comprising thepoly(vinyl acetal) resin having the lower residual hydroxyl content, theresin layer can have a glass transition temperature of not more than 25,not more than about 20, not more than about 15, not more than about 10,not more than about 5, not more than about 0, not more than about −5, ornot more than about −10° C., and a refractive index of at least about1.465, at least about 1.470, at least about 1.475, at least about 1.480,at least about 1.485, at least about 1.495, or at least about 1.500,each measured as described previously. The plasticizer content of thislayer, in some embodiments, can be at least about 50, at least about 55,at least about 60, at least about 65 phr and/or not more than about 120,not more than about 110, not more than about 90, not more than about 85,not more than about 80, or not more than about 75 phr, or in the rangeof from about 50 to about 120, about 55 to about 110, about 60 to about90, about 65 to about 75 phr.

When the solid RI additive is present in the resin layer that comprisesthe poly(vinyl acetal) resin having a higher residual hydroxyl content,the layer can have a glass transition temperature of at least about 26,at least about 30, at least about 33, or at least about 35° C. In someembodiments, the layer can have a refractive index of at least about1.470, at least about 1.475, at least about 1.480, at least about 1.485,at least about 1.490, at least about 1.500, at least about 1.510. Theplasticizer content of this layer, according to some embodiments, can beless than 50 phr, not more than about 45 phr, not more than about 40phr, not more than about 30, or not more than about 20 phr.

Resin compositions, layers, and interlayers formulated according tovarious embodiments of the present invention to include at least twopoly(vinyl acetal) resins and an RI balancing agent can exhibit enhancedoptical properties without sacrificing other properties such as impactresistance and acoustic performance. As discussed above, due todifferences in properties or composition of the resins, such as, forexample, residual hydroxyl content, residual acetate content, oraldehyde residues, identical blends of the same resins formulatedwithout the RI balancing agent may provide compositions, layers, andinterlayers with reduced optical performance.

Clarity is one parameter used to describe the optical performance ofcompositions, layers, and interlayers described herein and may bedetermined by measuring haze value or percent. Haze value represents thequantification of light scattered by a sample in contrast to theincident light. In some embodiments, the resin blends, layers, andinterlayers described herein may have a haze value of less than 5percent, less than about 4 percent, less than about 3 percent, less thanabout 2 percent, less than about 1, or less than about 0.5 percent, asmeasured in accordance with ASTM D1003-13—Procedure B using IlluminantC, at an observer angle of 2 degrees. The test is performed with aspectrophotometer, such as a Hunterlab UltraScan XE instrument(commercially available from Hunter Associates, Reston, Va.), on apolymer sample having a thickness of 0.76 mm, which has been laminatedbetween two sheets of clear glass each having a thickness of 2.3 mm(commercially available from Pittsburgh Glass Works of Pennsylvania).

In some embodiments, haze value is very low, e.g., less than 5 percent,less than about 4 percent, less than about 3 percent, less than about 2percent, less than about 1, or less than about 0.5 percent, however,when a bright light is shone on the laminates from behind, an opticaldefect appearing as a “milky haze,” can be seen when the laminates areviewed at wide angles (>30°). The presence or absence of such a “milkyhaze” is characterized herein by the HLD haze value. HLD haze ismeasured by a HLD haze measurement apparatus, which is constructed witha tungsten halogen light source, a sample holder, a goniometer with alight detector mounted on. The HLD haze measurement apparatus iscalibrated using a set of HLD standard laminates having a totalthickness of 8.3 mm (5 layers of 0.76 mm interlayer) between two 2.3-mmclear glass sheets representing HLD Haze grades 0, 1, 2, and the like,with increasing values indicating increased HLD haze. In thismeasurement, laminate was made with clear glass having thickness ofabout 2.3 mm by normal autoclave lamination process. After theautoclave, the laminate was placed at room temperature overnight. Thescattered light intensity at a scatted angle of 45° is collected from atesting laminate sample at room temperature using the HLD hazemeasurement apparatus, and HLD haze is calculated using computersoftware and reported at a nominal total laminate thickness.

Additionally, the resin layers and interlayers described herein may havea mottle value of not more than 3, not more than 2, or not more than 1.Mottle is another measure of optical quality, which is detected as atexture or graininess. Mottle is a visual defect if the level is toohigh or too severe, thereby causing objectionable visual appearance.Mottle is assessed and categorized by a side-by-side qualitativecomparison of shadowgraph projections for a test laminate with a set ofstandard laminate shadowgraphs that represent a series, or scale, ofmottle values ranging from 1 to 4, with 1 representing a standard of lowmottle (i.e., a low number of disruptions) and 4 representing a standardof high mottle (i.e., a high number of disruptions). High mottle isgenerally considered objectionable, particularly in automotive andarchitectural applications. Optionally, a model laminate having a singlelayer interlayer with zero mottle (no mottle) is used to facilitate theevaluation in a test laminate that has a mottle rating lower than thescale of the standard set, such as lower than a rating of 1. A testlaminate that shows a shadowgraph projection similar to that of azero-mottle laminate is assessed to have a mottle rating of zero. Thetest laminate is prepared with two sheets of clear glass each having athickness of 2.3 mm (commercially available from Pittsburgh Glass Worksof Pennsylvania) and an interlayer. The interlayer typically has arandom rough surface R_(z) of about 35 to 40 microns and thickness of0.76 to 0.86 mm.

The mottle values provided herein were determined using a Clear MottleAnalyzer (CMA) that includes a xenon arc lamp, a sample holder, aprojection screen, and a digital camera. The xenon arc lamp is used toproject a shadowgraph of a laminated sample onto the screen and thecamera is configured to capture an image of the resulting shadowgraph.The image is then digitally analyzed using computer imaging software andcompared to images of previously-captured standard samples to determinethe mottle of the sample. A method of measuring mottle using a CMA isdescribed in detail in U.S. Patent Application Publication No. US2012-0133764.

Another parameter used to determine the optical performance istransparency, or percent visual transmittance (% T_(vis)), which ismeasured using a spectrophotometer, such as a HunterLab UltraScan EX, inaccordance with ASTM D1003, Procedure B using Illuminant C at anobserver angle of 2°. The values provided herein were obtained byanalyzing a glass laminate samples having an interlayer thickness ofabout 0.76 mm and a clear glass thickness of 2.3 mm (commerciallyavailable from Pittsburgh Glass Works of Pennsylvania). In someembodiments, the resin layers and interlayers of the present inventioncan have a percent visual transmittance of at least about 70, at leastabout 75, at least about 80, at least about 81, at least about 82, atleast about 83, at least about 84, at least about 85, at least about85.5, at least about 86, at least about 86.5, at least about 87, atleast about 87.5, at least about 88, or at least about 88.5 percent.More specifically, the resin layers and interlayers of the presentinvention have a % T_(vis) of greater than 85 for the interlayerscontaining only additives of ACAs, UV stabilizers, and antioxidant, orgreater than 80% for the interlayers containing additional additivessuch as pigments, IR absorbers or blockers as mentioned above. Polymerinterlayers containing high levels of pigments and/or dyes may havelower % T_(vis) values as desired, such as in mass pigmented or coloredpolymer interlayers.

In addition to exhibiting one or more optical properties within theranges above, the resin layers and interlayers described herein may alsoexhibit acoustic properties within a desirable range. In someembodiments, as discussed above, at least a portion of a resin layer orinterlayer may have a glass transition temperature of not more than 25,not more than about 20, not more than about 15, not more than about 10,not more than about 5, not more than about 0, not more than about −5, ornot more than about −10° C., which may facilitate acoustic performanceof the layer or interlayer. At the same time, at least a portion of thelayer or interlayer may have a glass transition temperature of at leastabout 26, at least about 30, at least about 35° C., which may facilitateimpact resistance properties and strength.

In some embodiments, a resin layer or interlayer according to thepresent invention may have a tan delta value of at least about 0.70. Tandelta is the ratio of the loss modulus (G″) in Pascals to the storagemodulus (G′) in Pascals of a specimen measured by Dynamic MechanicalThermal Analysis (DMTA). The DMTA is performed with an oscillationfrequency of 1 Hz under shear mode and a temperature sweep rate of 3°C./min. The peak value of the G″/G′ curve at the glass transitiontemperature is the tan delta value. Resin layers or interlayers asdescribed according to various embodiment herein can have a tan delta ofat least about 1.0, at least about 1.05, at least about 1.10, at leastabout 1.25, at least about 1.50, at least about 1.75, at least about2.0, or at least about 2.25.

Additionally, the resin layers and interlayers can have a damping lossfactor, or loss factor, of at least about 0.10, at least about 0.15, atleast about 0.17, at least about 0.20, at least about 0.25, at leastabout 0.27, at least about 0.30, at least about 0.33, or at least about0.35. Loss factor is measured by Mechanical Impedance Measurement asdescribed in ISO Standard 16940. A polymer sample is laminated betweentwo sheets of clear glass, each having a thickness of 2.3 mm, and isprepared to have a width of 25 mm and a length of 300 mm. The laminatedsample is then excited at the center point using a vibration shaker,commercially available from Brüel and Kjær (Nærum, Netherlands) and animpedance head (Brüel and Kjær) is used to measure the force required toexcite the bar to vibrate and the velocity of the vibration. Theresultant transfer function is recorded on a National Instrument dataacquisition and analysis system and the loss factor at the firstvibration mode is calculated using the half power method. In someembodiments, when the RI balancing agent is a high RI plasticizer, thelayer or interlayer may have a loss factor greater than 0.25, greaterthan 0.27, greater than 0.30, or greater than 0.35 at 20° C., while, inother embodiments, when the RI balancing agent is a solid RI additive orresidues of at least one high RI aldehyde, the layer or interlayer mayhave a loss factor of at least about 0.10, at least about 0.15, at leastabout 0.20, at least about 0.25, or at least about 0.30 at 20° C.

“Sound transmission loss” (STL) is determined for a laminate of thepresent invention or comparative panel of fixed dimensions with ASTM E90(2009) at a fixed temperature of 20° C. A “Reference Panel” of 2.3 mmclear glass//“Reference interlayer”//2.3 mm clear glass is measured tohave STL of 31 dB at the coincident frequency (3,150 Hz), wherein the“Reference Interlayer” is produced by mixing and melt-extruding 100parts poly(vinyl butyral) resin having a residual hydroxyl content of 18to 19 wt. % and a vinyl acetate residue of 2 wt. %, 38 parts by weightof 3GEH plasticizer, and other common additives (as described above).The reference interlayer has a thickness of 0.76 mm and a glasstransition temperature of 30° C. The interlayers of the presentinvention or the comparative interlayers are laminated with 2.3 mm clearglass according to the method described above for making the reference(or test) laminated glass panel. The panel has dimensions of 50 cm by 80cm. The STL of the test panel at the coincident frequency of the“Reference Panel” (e.g., STL at 3,150 Hz) is used to assess the soundinsulation property of the panel.

Similar to the resin blend of two distinct resins of the firstpoly(vinyl acetal) resin and the second poly(vinyl acetal) resin,blending two or more distinct resin layers or interlayers can oftenresult in the new resin layer(s) or interlayer(s) having unexpectedproperties and performance attributes. For example, a resin layer orinterlayer having lower residual hydroxyl content and lower glasstransition temperature may be blended with another resin layer orinterlayer having higher residual hydroxyl content and higher glasstransition temperature, resulting a new resin layer or interlayer havingsoft domains of lower glass transition temperature, which enhances itsacoustic performance, and stiff domains of higher glass transitiontemperature, which imparts enhanced processability, strength, and impactresistance to the resin layer or interlayer. Other example includesblending a single sheet interlayer and multilayer interlayer, blendingtwo multilayer interlayers, or blending one multilayer interlayer into aresin layer of another multilayer interlayer. In essence, the effectarising from blending two materials can also be achieved from blendingtwo or more resins, plasticizers, and other additives according to thecontents of the materials. As used herein, a “blend resin material” or“blend material” refers to the resin composition, resin layer orinterlayer to be blended into another resin composition, resin layer orinterlayer. In blending two resin layers or two interlayers, at leastone of the two materials to be blended can include the resin layer orinterlayer of the present invention. In other embodiments, bothmaterials can include the resin layers or interlayers of the presentinvention.

According to some embodiments, at least a portion of the resincompositions, layers, or interlayers described herein may compriseanother resins, layers, or interlayers. In some embodiments, at leastabout 0.5, at least about 1, at least about 5, at least about 10, atleast about 15, at least about 20, at least about 25, at least about 30,or at least about 50 percent of the total amount of resin in acomposition, layer, or interlayer can originate from a blend resinmaterial.

Often, when the type and/or amount of resins and plasticizers in theblend resin material differ substantially from the type and/or amount ofthe resin or plasticizer being produced, and into which the blend resinmaterial is being added, the optical performance, as determined by theclarity or haze, of the resulting resin composition, layer, orinterlayer that includes the blend resin material may be adverselyimpacted. According to embodiments of the present invention, resinlayers and interlayers that include higher levels of blend resinmaterial can be produced by utilizing one or more of the RI balancingagents discussed above.

When the RI balancing agent includes a high RI plasticizer, higheramounts of blend resin materials can be added to a process for producinga resin composition, layer, or interlayer described herein withoutreducing the clarity or increasing the haze of the final composition,layer, or interlayer. In some embodiments, the composition that includesblend materials can include a first poly(vinyl acetal) resin and asecond poly(vinyl acetal) resin, wherein one of the resins has aresidual hydroxyl content that can be at least 2 weight percent lowerthan the residual hydroxyl content of the other resin. Such acomposition may further include at least one high RI plasticizer havinga refractive index of 1.460, and, in some embodiments, more than 3percent of the combined amount of the first and second poly(vinylacetal) resins present in the composition, layer, or interlayer may haveoriginated from a blend composition, layer, or interlayer. Despite thedifference in residual hydroxyl contents of the first and secondpoly(vinyl acetal) resins, the composition that includes more than 0.5weight percent of blend resin materials may have a haze value of notmore than about 5, not more than about 4, not more than about 3, notmore than about 2, or not more than about 1, or not more than about 0.5.

The high RI plasticizer used as an RI balancing agent with blend resincompositions can have a refractive index within one or more of theranges described previously. The high RI plasticizer may be added duringproduction of the composition, layer, or interlayer along with the blendmaterial and/or at least a portion of the high RI plasticizer may bepresent in the blend resin material added to the process. Additionally,one or more other plasticizers may also be present in the resin materialbeing blended and/or in the resin composition, layer, or interlayerbeing produced, including, for example, those having a refractive indexless than about 1.450, less than about 1.445, or less than about 1.442,measured as described previously. In some embodiments, one or moreadditional high RI plasticizers may also be present in the blendmaterial and/or in the resin composition, layer, or interlayer intowhich the materials are being blended.

The resin composition that includes blended resin material as describedabove can be used to form layers and interlayers according to variousembodiments of the present invention. For example, the resin compositionincluding a blend resin material can be used to form a single monolithicinterlayer, or it may be used to form one or more layers of a multilayerinterlayer. When used in various layers and interlayers, additionalplasticizer may be added such that the total amount of plasticizerpresent in the resin layer or interlayer can be within the rangedescribed previously. Similarly, the glass transition temperature andrefractive indices of resin layers and interlayers formed from acomposition that includes a blend resin material may also be within theranges provided above. Additionally, resin layers and interlayers formedfrom a composition that includes blended materials may also exhibitacoustic properties as described previously and may be included in anyof the applications described below.

According to some embodiments, at least a portion of the resincompositions, layers, or interlayers described herein may comprise oneor more recycled resin materials, including, for example, recycledlayers or interlayers. As used herein, the term “recycled” means removedfrom and subsequently returned to a production line. Often, utilizingrecycled materials may adversely affect the optical performance of thefinal composition, layer, or interlayer, as determined by clarity orhaze, because of the different compositions and properties of thematerials being blended or combined. However, in some embodiments,layers or interlayers as described herein may include at least onerecycled resin material, while still exhibiting the same optical and/oracoustic properties as described herein. The type and/or amount ofrecycle resin material may fall within one or more of the rangesdescribed previously and the layer or interlayer may further include atleast one RI balancing agent. Additionally, the resin layers andinterlayers including recycled resin material may also have opticaland/or acoustic performance within one or more of the ranges describedbelow.

The resin compositions, layers, and interlayers described above may beproduced according to any suitable method. In various embodiments, themethod for producing these compositions, layers, and interlayers caninclude providing two or more poly(vinyl acetal) resins, blending atleast one resin with an RI balancing agent and, optionally, at least oneplasticizer or other additive, to form a blended composition, andforming a layer from the blended composition.

In some embodiments, the resins provided in the initial steps of themethod can be in the form of one or more poly(vinyl acetal) resins,while, in other embodiments, one or more resin precursors can also beprovided. In some embodiments, when two or more poly(vinyl acetal)resins are physically blended, the blending of the two resins cancomprise melt blending and may be performed at a temperature of at leastabout 140, at least about 150, at least about 180, at least about 200,at least about 250° C. In other embodiments, when the poly(vinyl acetal)resin components provided include resin precursors, the blending stepmay include reacting two or more aldehydes with a polyvinyl alcohol toprovide a single poly(vinyl acetal) resin having two or more aldehydemoieties. Additionally, a portion of the blending step can includeblending one or more of the resins with at least one plasticizer and/orwith one or more of the RI balancing agents described previously.

The resulting blended resins can then be formed into one or more resinlayers according to any suitable method. Exemplary methods of formingpolymer layers and interlayers can include, but are not limited to,solution casting, compression molding, injection molding, meltextrusion, melt blowing, and combinations thereof. Multilayerinterlayers including two or more resin layers may also be producedaccording to any suitable method such as, for example, co-extrusion,blown film, melt blowing, dip coating, solution coating, blade, paddle,air-knife, printing, powder coating, spray coating, and combinationsthereof. In various embodiments of the present invention, the layers orinterlayers may be formed by extrusion or co-extrusion. In an extrusionprocess, one or more thermoplastic polymers, plasticizers, and,optionally, at least one additive, including one or more RI balancingagents as described previously, can be pre-mixed and fed into anextrusion device. Other additives, such as ACAs, colorants, and UVinhibitors, which can be in liquid, powder, or pellet form, may also beused and may be mixed into the thermoplastic polymers or plasticizersprior to entering the extrusion device. These additives can beincorporated into the polymer resin and, by extension, the resultantpolymer sheet, thereby enhancing certain properties of the polymer layeror interlayer and its performance in the final multiple layer glasspanel or other end product.

In various embodiments, the thickness, or gauge, of the layers orinterlayers can be at least about 10, at least about 15, at least about20 mils and/or not more than about 100, not more than about 90, not morethan about 60, not more than about 50, or not more than about 35 mils,or it can be in the range of from about 10 to about 100, about 15 toabout 60, or about 20 to about 35 mils. In millimeters, the thickness ofthe polymer layers or interlayers can be at least about 0.25, at leastabout 0.38, at least about 0.51 mm and/or not more than about 2.54, notmore than about 2.29, not more than about 1.52, or not more than about0.89 mm, or in the range of from about 0.25 to about 2.54 mm, about 0.38to about 1.52 mm, or about 0.51 to about 0.89 mm. In some embodiments,the resin layers or interlayers can comprise flat polymer layers havingsubstantially the same thickness along the length, or longest dimension,and/or width, or second longest dimension, of the sheet, while, in otherembodiments, one or more layers of a multilayer interlayer, for example,can be wedge-shaped or can have a wedge-shaped profile, such that thethickness of the interlayer changes along the length and/or width of thesheet, such that one edge of the layer or interlayer has a thicknessgreater than the other. When the interlayer is a multilayer interlayer,at least one, at least two, or at least three of the layers of theinterlayer can be wedge-shaped. When the interlayer is a monolithicinterlayer, the polymer sheet can be flat or wedge shaped. Wedge-shapedinterlayers may be useful in, for example, heads-up-display (HUD) panelsin automotive and aircraft applications.

The resin compositions, layers, and interlayers according to embodimentsof the present invention may be utilized in a multiple layer panel thatcomprises a resin layer or interlayer and at least one rigid substrate.Any suitable rigid substrate may be used and in some embodiments may beselected from the group consisting of glass, polycarbonate, biaxiallyoriented PET, copolyesters, acrylic, and combinations thereof. When therigid substrate includes glass, the glass can be selected from the grouplisted previously. When the rigid substrate includes a polymericmaterial, the polymeric material may or may not include a hard coatsurface layer. In some embodiments, the multilayer panels include a pairof rigid substrates with the resin interlayer disposed there between.The panels can be used for a variety of end use applications, including,for example, for automotive windshields and windows, aircraftwindshields and windows, panels for various transportation applicationssuch as marine applications, rail applications, etc., structuralarchitectural panels such as windows, doors, stairs, walkways,balusters, decorative architectural panels, weather-resistant panels,such as hurricane glass or tornado glass, ballistic panels, and othersimilar applications.

When laminating the resin layers or interlayers between two rigidsubstrates, such as glass, the process can include at least thefollowing steps: (1) assembly of the two substrates and the interlayer;(2) heating the assembly via an IR radiant or convective device for afirst, short period of time; (3) passing the assembly into a pressurenip roll for the first de-airing; (4) heating the assembly for a shortperiod of time to about 60° C. to about 120° C. to give the assemblyenough temporary adhesion to seal the edge of the interlayer; (5)passing the assembly into a second pressure nip roll to further seal theedge of the interlayer and allow further handling; and (6) autoclavingthe assembly at temperature between 135° C. and 150° C. and pressuresbetween 150 psig and 200 psig for about 30 to 90 minutes. Other methodsfor de-airing the interlayer-glass interface, as described according tosome embodiments in steps (2) through (5) above include vacuum bag andvacuum ring processes, and both may also be used to form interlayers ofthe present invention as described herein.

In some embodiments, the multiple layer panel may include at least onepolymer film disposed on the layer or interlayer, forming a multiplelayer panel referred to as a “bilayer.” In some embodiments, theinterlayer utilized in a bilayer may include a multilayer interlayer,while, in other embodiments, a monolithic interlayer may be used. Theuse of a polymer film in multiple layer panels as described herein mayenhance the optical character of the final panel, while also providingother performance improvements, such as infrared absorption. Polymerfilms differ from polymer layers or interlayers in that the films alonedo not provide the necessary penetration resistance and glass retentionproperties. The polymer film can also be thinner than the sheet, and mayhave a thickness in the range of from 0.001 to 0.25 mm. Poly(ethyleneterephthalate) (“PET”) is one example of a material used to form thepolymer film.

The following examples are intended to be illustrative of the presentinvention in order to teach one of ordinary skill in the art to make anduse the invention and are not intended to limit the scope of theinvention in any way.

EXAMPLES

The following Examples describe the preparation of several resincompositions, layers, and interlayers that include various poly(vinylacetal) reins. As described below, several tests performed on many ofthe compositions, layers, and interlayers were used to evaluate theacoustic and optical properties of several comparative and inventivematerials.

Example 1: Preparation of High Refractive Index Poly(Vinyl Acetal)Resins

Several comparative poly(vinyl acetal) resins, referred to asComparative Resins CR-1 through CR-12 in Table 2 below, were prepared byacetalizing polyvinyl alcohol with one or more aldehydes includingn-butyraldehyde (nBuCHO; RI=1.377), iso-butyraldehyde (iBuCHO;RI=1.374), and 2-ethylhexyl aldehyde (2EHCHO; RI=1.414). The compositionof the resulting resins were measured using either the ASTM D1396 orFT-IR/SEC method described in detail previously. The refractive index ofseveral of the resins was also measured according to the methodsdescribed previously, and the results are provided in Table 2, below.

TABLE 2 Properties of Several Comparative Poly(vinyl acetal) ResinsResidual Residual Residual Resin Residual Residual Polyvinyl PolyvinylPolyvinyl Refractive Hydroxyl Acetate nBuCHO iBuCHO 2EHCHO Index Resin(wt %) (wt %) (wt %) (wt %) (wt %) (nD25) CR-1 21 1 78 — — 1.491 CR-2 191 80 — — 1.490 CR-3 19 1 46 — 34 1.489 CR-4 16 1 83 — — 1.488 CR-5 15 139 — 45 1.487 CR-6 13 1 86 — — 1.486 CR-7 12 18 70 — — 1.481 CR-8 12 1276 — — nd CR-9 12 10 78 — — 1.483 CR-10 11 1 88 — — 1.485 CR-11 12 1 —88 — nd CR-12 13 1 — 86 — nd nd = not determined

Additionally, several poly(vinyl acetal) resins according to embodimentsof the present invention were also prepared in a similar manner. Theseinventive resins, referred to as Disclosed Resins DR-1 through DR-21 inTable 3, were formed by acetalizing polyvinyl alcohol with mixtures ofn-butyraldehyde and various high refractive index aldehydes, includingbenzaldehyde (BzCHO RI=1.545), cinnamaldehyde (CCHO; RI=1.620),4-chlorobenzaldehyde (4-CIBzCHO; RI=1.585), 2-phenylpropionaldehyde(2PHPrCHO; RI=1.517), and hydrocinnamaldehyde (HCCHO; RI=1.523). Therefractive index of several of the Disclosed Resins was also determinedand the results are summarized in Table 3, below.

TABLE 3 Properties of Disclosed Resins Resin Residual Residual AldehydeHCCHO/ CCHO/ 2PhPrCHO/ BzCHO/ 4ClBzCHO/ Refractive Hydroxyl AcetateComponent BuCHO = BuCHO = BuCHO = BuCHO BuCHO = HCCHO/ Index Resin (wt%) (wt %) (wt %) (mol/mol) (mol/mol) (mol/mol) (mol/mol) (mol/mol)iBuCHO (nD25) DR-1 11 1 88  5/95 — — — — — 1.496 DR-2 11 1 88 10/90 — —— — — 1.500 DR-3 11 1 88 15/85 — — — — — 1.504 DR-4 11 1 88 20/80 — — —— — 1.510 DR-5 11 1 88 25/75 — — — — — 1.511 DR-6 11 1 88 50/50 — — — —— 1.528 DR-7 11 1 88 100/0  — — — — — 1.552 DR-8 19 1 80 10/90 — — — — —nd DR-9 19 1 80 25/75 — — — — — nd DR-10 19 1 80 50/50 — — — — — ndDR-11 19 1 80 100/0  — — — — — nd DR-12 12 18 70 25/75 — — — — — ndDR-13 12 10 78 25/75 — — — — — nd DR-14 17 1 82 — 25/75 — — — — 1.507DR-15 15 1 84 — — 25/75 — — — 1.505 DR-16 14 1 85 — — 25/75 — — — 1.503DR-17 18 1 81 — — — 25/75 — — 1.507 DR-18 14 1 85 — — — 25/75 — — 1.501DR-19 20 1 79 — — — — 25/75 — 1.507 DR-20 14 1 85 — — — — 25/75 — 1.509DR-21 11 1 88 — — — — — 25/75 nd nd = not determined

As shown in Tables 2 and 3, above, polyvinyl acetal resins comprisingresidues of at least one high refractive index aldehyde, including thoselisted above, tend to exhibit higher refractive indices than thosecomprising residues of aldehydes such as n-butyraldehyde,iso-butyraldehyde, and 2-ethylhexyl aldehyde.

Example 2: Preparation of High Refractive Index Resin Interlayers

Several Comparative and Disclosed Interlayers were formed by mixing andmelt blending several of the Comparative Resins listed in Table 2 andseveral of the Disclosed Resins listed in Table 3 above, with varyingamounts of the plasticizer triethylene glycol bis(2-ethylhexanoate)(3GEH). The composition, refractive index, and glass transitiontemperature of each of the resulting interlayers, referred to asComparative Interlayers CL-1 through CL-14 and Disclosed InterlayersDL-1 through DL-26, were measured as described previously, and theresults are respectively summarized in Tables 4 and 5, below.

TABLE 4 Properties of Several Comparative Interlayers Refractive IndexInterlayer Resin Plasticizer (phr) (nD25) T_(g) (° C.) CL-1 CR-1 341.478 36 CL-2 CR-2 38 1.477 30 CL-3 CR-3 38 1.475 28 CL-4 CR-4 50 1.47217 CL-5 CR-4 30 1.477 30 CL-6 CR-5 75 1.468 6 CL-7 CR-6 75 1.467 2 CL-8CR-7 75 1.464 −4 CL-9 CR-8 75 1.466 −3 CL-10 CR-9 75 1.465 −3 CL-11CR-10 75 1.466 −2 CL-12 CR-10 50 1.47 12 CL-13 CR-11 75 nd nd CL-14CR-12 75 nd nd nd = not determined

TABLE 5 Properties of Several Disclosed Interlayers Plasticizer contentSheet Refractive Interlayer Resin (phr) Index (nD25) T_(g) (° C.) DL-1DR-1 75 1.473 1 DL-2 DR-1 50 1.479 12 DL-3 DR-2 75 1.475 0 DL-4 DR-3 751.477 0 DL-5 DR-4 75 1.480 1 DL-6 DR-5 75 1.482 1 DL-7 DR-6 75 1.490 2DL-8 DR-7 75 1.506 3 DL-9 DR-14 75 1.480 12 DL-10 DR-15 75 1.478 11DL-11 DR-16 75 1.477 7 DL-12 DR-17 75 1.480 22 DL-13 DR-18 75 1.476 12DL-14 DR-19 75 1.480 17 DL-15 DR-20 75 1.479 12 DL-16 DR-12 75 nd ndDL-17 DR-13 75 nd nd DL-18 DR-21 75 nd nd DL-19 DR-8 38 1.477 30 DL-20DR-9 38 1.487 nd DL-21 DR-10 38 1.501 nd DL-22 DR-11 38 1.525 nd DL-23DR-5 38 nd nd DL-24 DR-5 50 1.488 nd DL-25 DR-5 60 1.484 2 DL-26 DR-7 38nd nd nd = not determined

As shown in Tables 4 and 5, above, Disclosed Interlayers utilizinghigher refractive index Disclosed Resins from Table 3 exhibit higherrefractive indices than Comparative Interlayers formulated with lowerrefractive index resins, such as the Comparative Resins listed in Table2. Additionally, as shown by comparison of Disclosed Interlayers DL-1and DL-2 and DL-6 and DL-23 through DL-25, the amount of plasticizerused to form an interlayer affects both the glass transition temperatureand refractive index of the layer, although not necessarily to the sameextent for all resins. For example, as shown by the comparison of DL-1(75 phr 3GEH; Disclosed Resin 1) and DL-2 (50 phr 3GEH; Disclosed Resin1), reducing the amount of plasticizer by about 33 percent increases theglass transition temperature of the interlayer by 11° C. (from 1° C. to12° C.), and increases the refractive index by 0.006 (from 1.473 to1.479). However, as shown by the comparison of DL-25 (60 phr 3GEH;Disclosed Resin 5) and DL-6 (75 phr of 3GEH; Disclosed Resin 5),reducing the plasticizer content in layers formed by this resinincreases the glass transition temperature by only 1° C. (from 1° C. to2° C.), while increasing the refractive index by only 0.002 (from 1.482to 1.484).

Example 3: Preparation of Interlayers Using High Refractive Index Resins

Several of the Comparative and Disclosed Interlayers formed in Example 2and respectively summarized in Tables 4 and 5, above, were used tocreate several Comparative and Disclosed Multilayer Interlayers. Eachmultilayer interlayer included a pair of outer “skin” layers, having atotal thickness of 28 mils, sandwiching an inner “core” layer having athickness of 5 mils, usually formed of a resin having a lower residualhydroxyl content. The composition and several properties of theinterlayers including refractive index, glass transition temperature,mottle, and loss factor, were measured as described above, and theresults for the Comparative Multilayer Interlayers (CI-1 to CI-16) andDisclosed Multilayer Interlayers (DI-1 to DI-29) are summarized inTables 6 and 7, below.

TABLE 6 Properties of Several Comparative Multilayer InterlayersRefractive Δ Refractive Index of Loss Inter- Resin Layer T_(g) (° C.)Refractive Index Index Interlayer Factor at layer Skin 1 Core Skin 2Skin 1 Core Skin 2 Skin 1 Core Skin 2 (Skin − Core) (nD25) Mottle 20° C.CI-1 CL-2 CL-7 CL-2 30 2 30 1.477 1.467 1.477 0.010 1.475 4 0.29 CI-2CL-2 CL-11 CL-2 30 −2 30 1.477 1.466 1.477 0.011 1.475 5 0.33 CI-3 CL-2CL-8 CL-2 30 −4 30 1.477 1.464 1.477 0.013 1.475 5 nd CI-4 CL-1 CL-9CL-1 36 −3 36 1.478 1.466 1.478 0.012 1.477 5 nd CI-5 CL-1 CL-8 CL-1 36−4 36 1.478 1.464 1.478 0.014 nd 5 0.36 CI-6 CL-2 CL-9 CL-2 30 −3 301.477 1.466 1.477 0.011 nd 5 nd CI-7 CL-1 CL-11 CL-1 36 −2 36 1.4781.466 1.478 0.012 1.477 5 0.35 CI-8 CL-2 CL-10 CL-2 30 −3 30 1.477 1.4651.477 0.012 nd 5 0.31 CI-9 CL-1 CL-7 CL-1 36 2 36 1.478 1.467 1.4780.011 nd 5 nd CI-10 CL-1 CL-10 CL-1 36 −3 36 1.478 1.465 1.478 0.013 nd5 nd CI-11 CL-2 CL-13 CL-2 30 nd 30 nd nd nd nd nd >5 nd CI-12 CL-2CL-14 CL-2 30 nd 30 nd nd nd nd nd >5 nd CI-13 CL-1 CL-13 CL-1 36 nd 36nd nd nd nd nd >5 nd CI-14 CL-1 CL-14 CL-1 36 nd 36 nd nd nd nd nd >5 ndCI-15 CL-2 DL-7 CL-2 30 2 30 1.477 1.490 1.477 −0.013 1.479 >5 nd CI-16CL-2 DL-8 CL-2 30 3 30 1.477 1.506 1.477 −0.029 1.481 >5 nd nd = notdetermined

TABLE 7 Properties of Some Disclosed Multilayer Interlayers Δ RefractiveRefractive Inter- Resin Layer T_(g) (° C.) Refractive Index (nD25) IndexIndex of layer Skin 1 Core Skin 2 Skin 1 Core Skin 2 Skin 1 Core Skin 2(Skin − Core) Interlayer Mottle DI-1 CL-2 DL-1 CL-2 30 1 30 1.477 1.4731.477 0.004 1.476 1 DI-2 CL-2 DL-4 CL-2 30 0 30 1.477 1.477 1.477 0.0001.477 1 DI-3 CL-5 DL-6 CL-5 30 1 30 1.477 1.482 1.477 −0.005 1.478 ndDI-4 CL-2 DL-6 CL-2 30 1 30 1.477 1.482 1.477 −0.005 nd <1 DI-5 CL-1DL-6 CL-1 36 1 36 1.478 1.482 1.478 −0.004 nd <1 DI-6 CL-2 DL-3 CL-2 300 30 1.477 1.475 1.477 0.002 nd <1 DI-7 CL-2 DL-5 CL-2 30 1 30 1.4771.480 1.477 −0.003 nd <1 DI-8 CL-2 DL-6 CL-1 30 1 36 1.477 1.482 1.478−0.005 nd <1 DI-9 CL-2 DL-6 CL-5 30 1 30 1.477 1.482 1.477 −0.005 nd <1DI-10 CL-2 DL-16 CL-2 30 nd 30 1.477 nd 1.477 nd nd <1 DI-11 CL-2 DL-17CL-2 30 nd 30 1.477 nd 1.477 nd nd <1 DI-12 CL-1 DL-16 CL-1 36 nd 361.478 nd 1.478 nd nd <1 DI-13 CL-1 DL-17 CL-1 36 nd 36 1.478 nd 1.478 ndnd <1 DI-14 CL-2 DL-18 CL-2 30 nd 30 1.477 nd 1.477 nd nd <1 DI-15 CL-1DL-18 CL-1 36 nd 36 1.478 nd 1.478 nd nd <1 DI-16 DL-19 DL-24 DL-19 30 130 1.477 1.488 1.477 −0.005 1.478 <1 DI-17 CL-2 DL-9 CL-2 30 12 30 1.4771.480 1.477 −0.003 nd <1 DI-18 CL-2 DL-10 CL-2 30 11 30 1.477 1.4781.477 −0.001 nd <1 DI-19 CL-2 DL-11 CL-2 30 7 30 1.477 1.477 1.477 0.000nd <1 DI-20 CL-2 DL-12 CL-2 30 22 30 1.477 1.480 1.477 −0.003 nd <1DI-21 CL-2 DL-13 CL-2 30 12 30 1.477 1.476 1.477 0.001 nd <1 DI-22 CL-2DL-14 CL-2 30 17 30 1.477 1.480 1.477 −0.003 nd <1 DI-23 CL-2 DL-15 CL-230 12 30 1.477 1.479 1.477 −0.002 nd <1 DI-24 DL-20 DL-7 DL-20 nd 2 nd1.487 1.490 1.487 −0.003 nd <1 DI-25 DL-21 DL-7 DL-21 nd 2 nd 1.5011.490 1.501 −0.011 nd >5 DI-26 DL-22 DL-7 DL-22 nd 2 nd 1.525 1.4901.525 −0.035 nd >5 DI-27 DL-20 DL-8 DL-20 nd 3 nd 1.487 1.506 1.487−0.009 nd 3 DI-28 DL-21 DL-8 DL-21 nd 3 nd 1.501 1.506 1.501 −0.005 nd<1 DI-29 DL-22 DL-8 DL-22 nd 3 nd 1.525 1.506 1.525 −0.019 nd >5 nd =not determined

As shown in Table 6, above, interlayers formed from skin and core layershaving refractive index differences of 0.010 or more exhibited opticaldefects, as indicated by the mottle values greater than 5. As shown inTable 7, however, interlayers formed from skin and core layers havingrefractive index differences of less than 0.010 exhibited low mottlevalues of 1 or less. Additionally, as shown in Table 7, such low mottlevalues were achievable by interlayers having a core layer with a higheror lower refractive index than the skin layer, as long as the absolutevalue of the difference between the refractive indices of adjacentlayers was less than 0.010. Also as shown in Table 7, interlayers formedfrom skin and core layers both having high RI aldehyde residues andhaving refractive index differences of greater than 0.010 exhibited highmottle values of 5 or greater.

Example 4: Stability of Multilayer Interlayers

Two Comparative Multilayer Interlayers, CI-2 and CI-7, and two DisclosedMultilayer Interlayers, DI-4 and DI-5, prepared as described in Examples1-3 above, were tested to determine the relative stability of theinterlayers over time. Net plasticizer migration, which was measured bycomparing the glass transition temperatures of each layer at an initialtime (t=0) and after the layers have achieved equilibrium. The resultsare summarized in Table 8, below.

TABLE 8 Net Plasticizer Migration and Properties of ExemplaryComparative and Disclosed Interlayers T_(g) at T_(g) at Δ t = 0Equilibrium Δ T_(g) Refractive (° C.) (° C.) (° C.) Index Inter- T_(g)T_(g) T_(g) T_(g) Δ T_(g) Δ T_(g) (Skin − Mot- layer Skin Core Skin CoreSkin Core Core) tle CI-2 36 4.2 36 4.6 0.0 0.4 0.011 >5 DI-4 36 1.4 36.41.4 0.4 0.0 −0.005 <1 CI-7 42.5 2.2 42.5 1.4 0.0 −0.8 0.012 >5 DI-5 40.90.2 41.7 −1.8 0.8 −2.0 −0.004 <1

Disclosed Interlayer DI-4 exhibited minimal changes in the glasstransition temperature of both the skin and core layers of theinterlayer at equilibrium. This indicates a minor amount of plasticizermigration between the skin and core layers of each of Interlayers CI-2,CI-7, and DI-4. Although Comparative Interlayers CI-2 and CI-7 may berelatively stable, both exhibited a mottle value greater than 5, whichwould be unacceptable for most optical applications. In contrast, themottle value exhibited by Disclosed Interlayer DI-4 was less than 1.

The slight decrease in glass transition temperature exhibited byDisclosed Interlayer DI-5 at equilibrium indicated that a small amountof plasticizer migrated from the skin layer to the core layer. Suchmigration could be alleviated by utilizing a smaller amount ofplasticizer in the skin layer or a larger amount in the core. Even so,the refractive index of the core layer and the skin layer of DisclosedInterlayer DI-5 differed by only 0.004 and, as a result, the interlayeralso exhibited a mottle value less than 1.

Example 5: Blend of Conventional Poly(Vinyl Acetal) Resins and HighRefractive Index Poly(Vinyl Acetal) Resins

Several Comparative and Disclosed Resins, prepared as described inExample 1 above, were mixed and melt-blended together with 38 phr of3GEH plasticizer to form Comparative Blended Layers CBL-16 and CBL-17and Disclosed Blended Layers DBL-27 and DBL-28. Comparative Resin LayerCL-2 is listed in Table 9. CL-15 was formulated with Comparative ResinCR-10 and 38 phr of 3GEH, while Disclosed Resin Layers DL-27 and DL-28were formulated with Disclosed Resins DR-3 and DR-5, respectively, and38 phr of 3GEH. The haze and percent visual transmittance (T_(vis)) foreach blended resin interlayer were measured, along with the haze andpercent visual transmittance. The results are provided in Table 9,below.

TABLE 9 Haze and Percent Visual Transmittance of Several Resin Layersnposition Plasticizer Property Inter- CR-2 CR-10 DR-3 DR-5 content Haze% layer (wt %) (wt %) (wt %) (wt %) (phr) (%) T_(vis) CL-2 100  — — — 380.5 87.7 CL-15 — 100 — — 38 0.5 87.8 CBL-16 96 4 — — 38 2.1 84.3 CBL-1789 11 — — 38 14.7 80.2 DBL-27 96 —  4 — 38 0.8 87.8 DBL-28 89 — —  11 380.6 87.8 DL-27 — — 100 — 38 0.5 87.7 DL-28 — — — 100 38 0.5 87.8

As shown in Table 9 above, Comparative Blended Interlayers CBL-16 andCBL-17, which were formed from a blend of Comparative Resins CR-2 andCR-10, exhibited high haze values and lower percent visual transmittancethan single resin layers of Comparative Resin CR-2 (Comparative LayerCL-2) or CR-10 (Comparative Interlayer CL-15). In contrast, DisclosedBlended Interlayers DBL-27 and DBL-28, which were formed from a blend ofComparative Resin CR-2 and a high refractive index Disclosed Resin(Resin DR-3 in Layer DBL-27 or Resin DR-5 in Layer DBL-28), exhibitedsubstantially the same haze and percent visual transmittance asComparative Interlayer CL-2, which was formulated with Comparative ResinCR-2 alone. Thus, addition of inventive high refractive index resins toa comparative interlayer does not reduce the optical quality of theresulting interlayer.

Example 6: Preparation of Interlayers Having High Refractive IndexAdditives

Several poly(vinyl acetal) resins were prepared by acetalizing polyvinylalcohol with n-butyraldehyde. The resins, which had different residualhydroxyl contents, were melt blended with varying amounts of a 3GEHplasticizer and used to form various layers of multilayer interlayers.Each interlayer had an inner “core” layer having a thickness of 5 milssandwiched between two outer “skin” layers, each having a thickness of14 mils. The poly(vinyl butyral) resin used to form the core layers hada hydroxyl content of 11 weight percent and the resin used for the skinlayers had a hydroxyl content of 19 weight percent. Both resins had aresidual acetate content of about 2 weight percent.

Comparative Interlayers CI-17 through CI-19 were formed with resinlayers plasticized with 3GEH, which was present in varying amounts inthe core and skin layers. In addition to the 3GEH, Disclosed InterlayersDI-30 through DI-38 also included varying amounts of two different highrefractive index additives, Benzoflex™ 2-45 (diethyleneglycoldibenzoate; commercially available from Eastman Chemical Company,Kingsport, Tenn.) (Additive A-1), which had a melting point of 28° C.and a refractive index of 1.542; and Benzoflex™ 352 (1,4-cyclohexanedimethanol dibenzoate; commercially available from Eastman ChemicalCompany) (Additive A-2), which had a melting point of 118° C. and arefractive index of 1.554. The refractive index and glass transitiontemperatures of each of the layers of Comparative Interlayers CI-17through CI-19 and Disclosed Interlayers DI-30 through DI-38 weremeasured and the results are summarized in Table 10 below.

TABLE 10 Properties of Several Comparative and Disclosed Interlayers ΔSkin Layers Core Layer Refractive Plasticizer High RI High RI TotalPlasticizer High RI High RI Total Index Inter- Content Additive AdditiveA + A:P T_(g) Content Additive Additive A + A:P T_(g) (Skin − layer (P)(phr) Type (A) (phr) P Ratio RI (° C.) (P) (phr) Type (A) (phr) P RatioRI (° C.) Core) CI-17 40 — — — 1.476 30 65.0 — — — 1.467 2.9 0.008 CI-1840 — — — 1.476 30 75.0 — — — 1.466 −2.0 0.010 CI-19 40 — — — 1.476 3085.0 — — — 1.465 −3.1 0.011 DI-30 20 A-1 20 40 1.0 1.492 29 32.5 A-132.5 65 1.0 1.488 4.2 0.004 DI-31 20 A-1 20 40 1.0 1.492 29 37.5 A-137.5 75 1.0 1.488 −0.6 0.004 DI-32 20 A-1 20 40 1.0 1.489 29 42.5 A-142.5 85 1.0 1.488 −3.3 0.004 DI-33 17.2 A-1 22.8 40 1.3 1.496 30 22.8A-1 42.2 65 1.9 1.494 5.2 0.002 DI-34 17.2 A-1 22.8 40 1.3 1.496 30 26.2A-1 48.8 75 1.9 1.494 2.4 0.002 DI-35 17.2 A-1 22.8 40 1.3 1.496 30 29.8A-1 55.2 85 1.9 1.494 −2.1 0.002 DI-36 20 A-2 20 40 1.0 1.493 34 27.5A-2 27.5 55 1.0 1.490 15.9 0.003 DI-37 20 A-2 20 40 1.0 1.493 34 35.0A-2 35.0 70 1.0 1.490 8.4 0.003 DI-38 20 A-2 20 40 1.0 1.493 34 42.5 A-242.5 85 1.0 1.491 1.8 0.002

As shown in Table 10, above, increasing the plasticizer content of thecore layer of an interlayer that only included a 3GEH plasticizerreduced the glass transition temperature of the layer, which,ultimately, would have improved its acoustic performance. However, suchan increase also widened the difference between the refractive indicesof the skin and core layers, thereby reducing the optical quality of theinterlayer. As shown by comparison with Disclosed Interlayers DI-30through DI-38 in Table 10, the refractive index of core layersformulated with an additional high refractive index additive, remainedfairly constant with increased plasticizer loading, while stillexhibiting a similar reduction in glass transition temperature. Theresult was an interlayer having core and skin layers with nearly thesame refractive index, which greatly reduced optical defects such asmottle. At the same time, the core layer also exhibited a sufficientlylow glass transition temperature, indicating that the core layer alsohad acoustic properties.

Example 7: Preparation of Core Layers Having Reactive High RefractiveIndex Additives

Several resin layers, used to simulate the inner core layer of amultilayer interlayer, were formed by melt blending a polyvinyln-butyral resin having a residual hydroxyl content of 11 weight percentand a residual acetate content of about 2 weight percent with varyingamounts of 3GEH plasticizer. Comparative Layer CL-16 included 75 phr of3GEH, while Disclosed Layers DL-29 through DL-31 were formulated withvarious mixtures of 3GEH and a reactive high refractive index additive(reactive high RI additive). The reactive high RI additive used inDisclosed Layers DL-29 and DL-30 (Additive A) wasdiphenyldimethoxysilane (commercially available as SID4535.0 fromGelest, Inc., Morrisville, Pa.), and the reactive high RI additive usedin Disclosed Layer DL-31 (Additive B) was phthalic anhydride(commercially available from Sigma Aldrich Co., St. Louis, Mo.). Therefractive index of Comparative Layer CL-16 and each of Disclosed LayersDL-29 through DL-31 was measured and the results are provided in Table11, below.

TABLE 11 Refractive Index of Comparative and Disclosed Core Resin LayersPlasticizer Additive A Additive B Content Content Content RefractiveIndex Resin Layer (phr) (phr) (phr) (nD25) CL-16 75 — — 1.466 DL-29 72 3— 1.468 DL-30 72 6 — 1.470 DL-31 72 — 3 1.470

As shown in Table 11, resin layers formed using 3GEH in combination withone or more reactive high refractive index additives had a higherrefractive index than resin layers formulated with only 3GEH. As aresult, when employed as an inner core layer in a multilayer interlayer,the Disclosed Layers DL-29 through DL-31 had a refractive index thatmore closely matched the refractive index of a skin layer formed ofpolyvinyl n-butyral (RI=1.477). As a result, multilayer interlayersformed with Disclosed Layers DL-29 through DL-31 as a core layer exhibitfewer optical defects than multilayer interlayers formed withComparative Layer CL-16 as an inner core layer.

Example 8: Various Interlayers with Resin Blends Having a HighRefractive Index Plasticizer

Two polyvinyl n-butyral resins, R-1 and R-2, were prepared according tothe procedure described above in Example 1. Resin R-1 had a residualhydroxyl content of 19 weight percent, while resin R-2 had a residualhydroxyl content of 11 weight percent. Both resins had residual acetatecontents of 2 weight percent. Several resin blends were prepared thatincluded varying amounts of resins R-1 and R-2 in order to simulatevarious blending rates. The blends were combined with 38 phr of aplasticizer selected from 3GEH (plasticizer P-1; RI=1.442), dioctylphthalate (plasticizer P-2; RI=1.485), a blend of 30 weight percent 3GEHand 70 weight percent Benzoflex® 2088, which is commercially availablefrom Eastman Chemical Company, Kingsport, Tenn., (plasticizer P-3;RI=1.506), and nonylphenyl tetraethylene glycol (plasticizer P-4;RI=1.500). The resulting plasticized resins were then formed into singlesheets that included both resins and the plasticizer. The refractiveindex, haze, and percent visual transmittance was determined for eachsheet and the results are provided in Table 12, below.

TABLE 12 Properties of Several Resin Blends Plasticizer P-1 PlasticizerP-2 Plasticizer P-3 Plasticizer P-4 Resin A Resin B RI of Haze T_(vis)RI of Haze T_(vis) RI of Haze T_(vis) RI of Haze T_(vis) (wt %) (wt %)Interlayer (%) (%) Interlayer (%) (%) Interlayer (%) (%) Interlayer (%)(%) 100 0 1.477 0.4 88.5 1.494 0.4 88.5 1.495 0.3 88.4 1.493 0.3 88.598.9 1.1 1.477 0.6 87.9 1.494 0.4 88.6 1.495 0.3 88.8 1.493 0.3 88.797.8 2.2 1.476 1.2 87.1 1.498 0.3 88.4 1.495 0.3 88.7 1.493 0.2 88.795.6 4.4 1.477 1.9 84.6 1.495 0.4 88.4 1.495 0.3 88.6 1.492 0.4 88.591.2 8.8 1.476 5.4 81.7 1.495 0.5 88.3 1.495 0.4 88.5 1.493 0.3 88.688.9 11.1 1.476 12.9 80.6 1.494 0.6 88.2 1.495 0.4 88.2 1.492 0.4 88.2

As shown in Table 12, above, although blended resin layers formulatedwith plasticizer P-1 maintained a substantially constant refractiveindex with increasing amounts of the lower hydroxyl content resin R-2,the optical properties of these resin blends having high levels of R-2worsened as the amount of R-2 increased. For example, as shown in Table12, the haze of blends that included more than 1.1 percent of resin R-2increased, while the percent visual transmittance of these blendsdecreased from 88.5 percent to 80.6 percent.

In contrast, the resin blends including more than 2.2 percent of resinR-2 that were plasticized with higher refractive index plasticizers P-2through P-4, each exhibited substantially the same haze value andpercent visual transmittance as blends having lower amounts of resinR-2. Therefore, it can be concluded that the resin blends utilizinghigher refractive index plasticizers, such as plasticizers P-2 throughP-4, may permit higher amounts of lower hydroxyl content resins withoutadversely impacting the optical properties of the final blend.

Example 9: Poly(Vinyl Butyral) Layers Including a High Refractive IndexPlasticizer

Several poly(vinyl n-butyral) layers were formed by combining and meltblending three different poly(vinyl n-butyral) resins (PVB-1 throughPVB-3) with different types and amounts of plasticizer. Each of theresins PVB-1 through PVB-3 had a different residual hydroxyl content,ranging from 11 to 20.4 weight percent, and all three resins had aresidual vinyl acetate content of 1 weight percent. Comparative LayersCL-17 through CL-19 were formulated with varying amounts of triethyleneglycol di-(2-ethylhexanoate) (“3GEH”; RI=1.442), while Disclosed LayersDL-32 through DL-37 included a mixture of 3GEH with Benzoflex™ 354(commercially available from Eastman Chemical Company, Kingsport,Tenn.)(RI=1.53). The refractive index of each layer was measured and theresults are summarized in Table 13, below.

TABLE 13 Several Poly(vinyl) Butyral Layers with Various PlasticizersPlasticizer Content Residual Ratio of Total hydroxyl 3GEH Benzoflex ™3GEH to plasticizer Refractive Resin content content 354 Benzoflex ™content Index Layer (wt %) (phr) (phr) 354 (phr) (nD25) CL-17 19 38 — —38 1.477 CL-18 19 38 — — 38 1.477 CL-19 11 75 — — 38 1.466 DL-32 20.430.1 12.9 30/70 43 1.484 DL-33 20.4 25.8 17.2 40/60 43 1.485 DL-34 20.421.5 21.5 50/50 43 1.488 DL-35 11 59.5 25.5 30/70 85 1.479 DL-36 11 5134 40/60 85 1.481 DL-37 11 42.5 42.5 50/50 85 1.486

As shown in Table 13, above, resin layers that included a highrefractive index plasticizer exhibited a higher refractive index thanthose that included only a low refractive index plasticizer.

Example 10: Preparation of Interlayers Having High Refractive IndexAdditives

Several of the Comparative and Disclosed Interlayers formed in Example 9and summarized in Table 13, above, were used to create severalComparative and Disclosed Multilayer Interlayers. Each multilayerinterlayer included a pair of outer “skin” layers, each having athickness of 14 mils, sandwiching an inner “core” layer, having athickness of 5 mils, formed of a resin having a lower residual hydroxylcontent. The composition and several properties of the multilayerinterlayers, including total plasticizer content, refractive index,glass transition temperature, mottle, and loss factor, were measured asdescribed above, and the results for the Comparative MultilayerInterlayers CI-20 and CI-21 and Disclosed Multilayer Interlayers DI-39through DI-41 are summarized in Table 14, below.

TABLE 14 Properties of Several Comparative and Disclosed InterlayersTotal Δ Inter- plasticizer Refractive Refractive T_(g) Loss layer SkinCore Skin content Index Index (° C.) Factor No Layer 1 Layer Layer 2(phr) (Skin − Core) (nD25) Skin Core Mottle at 20° C. CI-20 CL-17 CL-18CL-17 38 0.000 1.477 30 — 0 0.02 CI-21 CL-17 CL-19 CL-17 42.5 0.0111.475 35 3 5 0.32 DI-39 DL-32 DL-35 DL-32 48 0.005 1.484 38.8 2.6 0.40.41 DI-40 DL-33 DL-36 DL-33 48 0.004 1.486 39.6 4.7 0.4 0.39 DI-41DL-34 DL-37 DL-34 48 0.002 1.488 40.9 8.7 0.4 0.33

As shown in Table 14 above, interlayers formed from skin and core layershaving a refractive index difference greater than 0.010 exhibited moreoptical defects, as shown by the mottle value of 5. Additionally,Disclosed Interlayers D-39 through D-41, which utilized a highrefractive index plasticizer, exhibited a higher overall refractiveindex as compared to Comparative Interlayers CI-20 and CI-21, which onlyutilized a plasticizer having a refractive index less than 1.460, thedifference of refractive indices between skin and core is 0.005, and themottle is 0.4

Example 11: Incompatible Terephthalic Acid Based Plasticizer with HighRefractive Index

Di-2-ethylhexylterephthalate (DOTP) was used to make DisclosedInterlayers DL-38 through DL-47 in Table 16 below and these DisclosedInterlayers were used to make Disclosed Multilayer Interlayers, DI-42 toDI-46, also presented in Table 16 below.

TABLE 15 Abbreviations and Refractive Index of Several PlasticizersPlasticizer Chemical Name Refractive index (nD25) 3GEH triethyleneglycol di-2-ethylhexanoate 1.442 DOP Dioctyl phthalate 1.485 DINPDiisononyl phthalate 1.485 DOTP Di-2-ethylhexyl terephthalate 1.489 METPBis-(methoxyethyl) terephthalate 1.503 BETP Bis-(butoxyethyl)terephthalate 1.490 BEETP Bis-(butoxyethoxyethyl) terephthalate 1.487EETP Bis-(ethoxyethyl) terephthalate 1.497 EEETP Bis-(ethoxyethoxyethyl)terephthalate 1.493 2EH1ETP Bis-(2-ethylhexyloxyethyl) terephthalate1.483 2EHIP Bis-(2-ethylhexyl) iso-phthalate 1.486 2EH2ETPBis-(2-ethylhexyloxyethoxyethyl) terephthalate nd 2EHEBz2-ethylhexyloxyethyl benzoate 1.442 2EHEEBz 2-ethylhexyloxyethoxylethylbenzoate 1.483 EEEBz Ethoxyethoxyethyl benzoate 1.491 BEEBzButoxyethoxyethyl benzoate 1.487 BEEEBz Butoxyethoxyethoxyethyl benzoate1.489 DodBz Dodecyl benzoate 1.489 DPGDT Dipropylene glycol di-o-toluate1.527 TEGBzAc Triethylene glycol benzoate acetate 1.498 Benzoflex 9-88(B9-88) dipropylene glycol dibenzoate 1.528 Benzoflex B1046 (B1046)2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate 1.492 Benzoflex(B2088) Mixure of benzoic acid esters of DPG and DEG 1.538 BenzoflexB131 (B131) Isodecyl benzoate 1.488 Benzoflex B181 (B181) 2-ethylhexylbenzoate 1.489 Uniplex 400 (U400) Polypropylene glycol dibenzoate1.515-1.520 Benzoflex B354 (B354) 2,2,4-trimethyl-1,3-pentanedioldibenzoate 1.529 Benzoflex B284 (B284) Propylene glycol dibenzoate 1.544Benzoflex B2-45 (B2-45) Diethylyene glycol dibenzoate 1.542 Surfonc N-40Nonylphenyl tetraethylene glycol 1.5

TABLE 16 Interlayer Construction skin layer/core layer/skin layer Skinlayer Core Layer Multi- Residual Residual Refractive Residual layerhydroyxl acetate Plasticizer index of Stability hydroyxl Inter-Disclosed content content content Resin Layer of the Disclosed contentlayer Interlayer (wt. %) (wt. %) (phr) (nD25) Resin Layer Interlayer(wt. %) DI-42 DL-38 19 <2 38 1.490 exuded DL-43 11 DI-43 DL-39 19 <2 421.490 exuded DL-44 11 DI-44 DL-40 19 <2 48 1.489 exuded DL-45 11 DI-45DL-41 19 <2 54 1.489 exuded DL-46 11 DI-46 DL-42 19 <2 60 1.486 exudedDL-47 11 Core Layer Delta Multi- Residual Refractive Refractive layeracetate Plasticizer index of Stability Index Interlayer/ Inter- contentcontent Resin Layer of the (skin − core) Laminate layer (wt. %) (phr)(nD25) Resin Layer (nD25) Mottle Stability DI-42 <2 60 1.486 exude 0.004<1 exuded DI-43 <2 70 1.487 exude 0.003 <1 exuded DI-44 <2 80 1.486exude 0.004 <1 exuded DI-45 <2 90 1.486 exude 0.003 <1 exuded DI-46 <2100 1.486 exude 0.000 <1 exuded

As shown in Table 16, the di-2-ethylhexylterephthalate (DOTP)plasticizer used in poly(vinyl acetal) Disclosed Interlayers, DL-38through DL-47, formed sheets with high refractive indices but the layerswere not stable. Over time, the plasticizer exuded from the DisclosedInterlayers and Disclosed Multilayer Interlayers, resulting in theDisclosed Interlayers and Disclosed Multilayer Interlayers being underplasticized, which diminished the acoustic performance. Such exudationcan also cause contamination and handling issues. Dioctyl phthalate(DOP) and diisononyl phthalate (DINP) are additional high refractiveindex plasticizers that are effective in reducing the difference ofrefractive index between the skin and core layers in the multiple layerinterlayers but these multiple layer interlayers are not stable and willexude from the Disclosed Interlayers and are unable to impart thenecessary acoustic and mechanical properties. Novel plasticizers thathave both a high refractive index and are compatible with the poly(vinylacetal) resins when formed into Interlayers and Multilayer Interlayersare designed, synthesized, and examined in Examples 12 to 18. Names,respective abbreviations, and refractive indices as measured by nD25 ofnovel plasticizers are listed in Table 15 along with commerciallyavailable plasticizers examined in this invention.

Example 12: General Synthetic Procedure of Terephthalate, Benzoate, andMixed Benzoic Plasticizers with High Refractive Index

To a 4-neck 2 liter round bottom flask was charged with either dimethylterephthalate or methyl benzoate (limiting reactant) and an excess ofthe transesterification alcohol. Titanium isopropoxide catalyst was thenadded to the mixture. The round bottom was fitted with a Dean-Stark trapand a simple distillation head, which acted as the condenser for theprocess. A nitrogen sweep was established through the round bottom andcondenser. Overhead stirring distributed pot materials evenly throughoutthe reactions. Reaction temperatures were controlled via a Camilesystem. Desired temperatures varied depending on the boiling points ofstarting materials, e.g., about 140° C. to 240° C. The reaction wasmonitored by GC analysis. Once the GC analysis showed completeconversion of the limiting reagent to product with no residual methanol,the product material was treated with base washes using 10% (W/W 100 mL)solution of potassium hydroxide in DI water at 50° C. for approximately1.5 minutes. A pH of 14 confirmed neutralization of the catalyst andallowed for continuation to the next wash. The next wash solution was a6% (w/w 100 mL) sodium bicarbonate and DI water solution to removeunreacted starting material. The excess reagent was removed from themixture under vacuum, heat and nitrogen purge. After removing the excessreagent, the material in the flask could be analyzed by GC to make sureall excess alcohol or ether was removed as desired. The material wasfiltered through celite under vacuum with a Buchner funnel and a 1 litervacuum flask. The final product was weighed, placed in a sample bottle,and distributed for future experimental purposes.

Modifications to this procedure for the various plasticizer moleculessynthesized were made due to experimental conditions and relativereactivities.

Example 13: Terephthalic Acid Based Plasticizers with High RefractiveIndex

Several poly(vinyl acetal) Comparative Interlayers, referred to as CL-20through CL-22, and several resulting inventive Disclosed Interlayers,referred to as DL-48 through DL-63, are summarized in Table 17. Each ofthese poly(vinyl butyral) interlayers were formed by mixing one of twopoly(vinyl butyral) resins, one with about 19% residual hydroxyl groupsand the other with about 11% residual hydroxyl groups, with varyingamounts of terephthalic acid based plasticizers such asbis-(methoxyethyl) terephthalate (METP), bis-(butoxyethyl) terephthalate(BETP), bis-(butoxyethoxyethyl) terephthalate (BEETP),bis-(ethoxyethoxyethyl) terephthalate (EEETP),bis-(2-ethylhexyloxyethyl) terephthalate (2EH1ETP), andbis-(2-ethylhexyloxyethoxyethyl) terephthalate (2EH2ETP) as shown inTable 17. Both the thickness and the refractive index of the PVBInterlayers were measured and summarized in Table 17.

The Comparative and Disclosed Interlayers, CL-20 through CL-22 and DL-48through DL-63, were then used to create several Comparative andDisclosed Multilayer Interlayers. As explained in Example 3, eachmultilayer interlayer has a pair of outer “skin” layers sandwiching aninner “core” layer, usually formed of a resin having a lower residualhydroxyl content. The composition and several properties of themultilayer interlayers including refractive index, glass transitiontemperature, mottle, loss factor, were measured as described above andthe results for Comparative Multilayer Interlayers (CI-22 to CI-23) andDisclosed Multilayer Interlayers (DI-57 to DI-62) are summarized inTable 18 below.

TABLE 17 Terephthalic Acid Based Plasticizers Table 15: TerephthalicAcid Based Plasticizers Residual Residual vinyl hydroyxl acetate 3GEHMETP BETP BEETP Refractive Inter- content content content contentcontent content Thickness Index layer (wt. %) (wt. %) (phr) (phr) (phr)(phr) EEETP 2EH1ETP 2EH2ETP (mm) (nD25) CL-20 19 <2 38 — — — — — — 141.477 CL-21 19 <2 38 — — — — — — 5 1.477 CL-22 11 <2 75 — — — — — — 51.466 DL-48 19 <2 — 38 — — — — — 14 1.494 DL-49 11 <2 — 75 — — — — — 51.494 DL-50 19 <2 — — 41 — — — — 14 1.492 DL-51 19 <2 — — 43 — — — — 141.490 DL-52 11 <2 — — 76 — — — — 5 1.486 DL-53 19 <2 — — — 41 — — — 141.490 DL-54 19 <2 — — — 43 — — — 14 1.489 DL-55 21 <2 — — — 33 — — — 141.490 DL-56 21 <2 — — — 35.5 — — — 14 1.488 DL-57 11 <2 — — — 78 — — — 51.486 DL-58 19 <2 — — — — 38 — — 14 1.490 DL-59 11 <2 — — — — 75 — — 51.485 DL-60 19 <2 — — — — — 38 — 14 1.492 DL-61 11 <2 — — — — — 75 — 51.489 DL-62 19 <2 — — — — — — 38 14 1.493 DL-63 11 <2 — — — — — — 75 51.489

TABLE 18 Multilayer Interlayers Delta Refractive Glass Transition STL atMulti- Refractive Index of Temperature of Reference layer IndexMultilayer Multilayer Loss frequency Inter- Skin Core Skin Plasti- (skinlayer − Interlayer Interlayer (° C.) Factor 3,150 Hz layer layer 1 Layerlayer 2 cizer 1 core layer) (nD25) T_(g1) T_(g2) Mottle at 20° C. (dB)CI-22 CL-20 CL-21 CL-20 3GEH 0.000 1.477 30 — 0 0.02 31 CI-23 CL-20CL-22 CL-20 3GEH 0.011 1.475 30 −2 5 0.32 40 DI-47 DL-48 DL-49 DL-48METP 0.000 1.494 30 0 — — — DI-48 DL-50 DL-52 DL-50 BETP 0.006 1.491 321 0.8 0.37 — DI-49 DL-51 DL-52 DL-51 BETP 0.004 1.489 30 1 0.3 0.39 39DI-50 DL-53 DL-57 DL-53 BEETP 0.004 1.490 29 0 0.5 0.31 38 DI-51 DL-54DL-57 DL-54 BEETP 0.003 1.490 27 0 0.6 0.35 39 DI-52 DL-55 DL-57 DL-55BEETP 0.004 1.488 39 0 0.1 0.24 — DI-53 DL-56 DL-57 DL-56 BEETP 0.0021.489 37 0 0.3 0.28 — DI-54 DL-58 DL-59 DL-58 EEETP 0.005 1.489 32 3 — —— DI-55 DL-60 DL-61 DL-60 2EH1ETP 0.003 1.491 45 17 — — — DI-56 DL-62DL-63 DL-62 2EH2ETP 0.004 1.493 41 11 — — —

As shown in Table 17 and 18, polyvinyl acetal resins comprising at leastone high refractive index plasticizer, including those METP, BETP,BEETP, EEETP, 2EH1ETP, 2EH2ETP plasticizers listed above, tend toexhibit higher refractive indices than those comprising a lowerrefractive index plasticizer such as triethylene glycoldi-2-ethylhexanoate (3GEH). Comparative Multilayer Interlayer CI-22 is amonolithic PVB interlayer, which would behave in the same manner as atrilayer construction of uniform composition (having the same layercomposition for each layer). CI-22 has a delta RI of 0 between theinterlayers, a single glass transition temperature, no mottle level of0, little sound damping, and very low or poor sound transmission loss.Comparative Multilayer Interlayer CI-23, which is a multilayerinterlayer, has two glass transition temperatures, each corresponding tothe respective interlayers. CI-23 exhibits high sound damping andexcellent sound transmission loss but also has a high delta RI of 0.011and a corresponding high mottle of 5. High mottle is objectionable formost multilayer interlayers, particularly those used in applicationswhere good optical properties are critical or necessary. Additionally,as shown by comparison of Disclosed Multilayer Interlayers DI-47 throughDI-56, the higher refractive index plasticizer used in the interlayersgive a refractive index difference of less than 0.010 exhibited by a lowmottle values of 1 or less in addition to excellent damping and soundtransmission loss. These corresponding low mottle values were achievableby selecting interlayers having a core layer with a higher or lowerrefractive index than the skin layer, as long as the absolute value ofthe difference between the refractive indices of adjacent layers wasless than 0.010.

Example 14: Benzoic Acid Based Plasticizers with High Refractive Index

Several benzoic acid based plasticizers are listed by name with theirabbreviation and refractive index as measured by nD25 in Table 15 above.These benzoic acid based plasticizers can be mixed with poly(vinylacetal) resins to produce monolayers, bilayers, and trilayers. The highrefractive index demonstrated by these benzoic acid based plasticizers,combined with the ability for greater uptake of these plasticizers bythe poly(vinyl acetal) resins with a lower residual hydroxyl content,can be used minimize the difference in refractive indices for the coreand skin layers resulting in a less optical defects.

Ethoxyethoxyethyl benzoate (EEEBz), butoxyethoxyethyl benzoate (BEEBz),butoxyethoxyethoxyethyl benzoate (BEEEBz), 2-ethylhexyloxyethyl benzoate(2EHEBz), 2-ethylhexyloxyethoxylethyl benzoate (2EHEEBz), dodecylbenzoate (DodBz), were used to make Disclosed Interlayers DL-64 throughDL-75 in Table 19 below and these Disclosed Interlayers were used tomake Disclosed Multilayer Interlayers, DI-57 to DI-62, in Table 20below. Each Disclosed Multilayer Interlayer included a pair of outer“skin” layers, each having a thickness of 14 mils, sandwiching an inner“core” layer, having a thickness of 5 mils, formed by a resin having alower residual hydroxyl content.

TABLE 19 Benzoate Based Plasticizers Residual Residual vinyl Refractivehydroyxl acetate Plasticizer Index of content content content InterlayerInterlayer (wt. %) (wt. %) Plasticizers (phr) (nD25) CL-20 19 <2 3GEH 381.477 DL 64 19 <2 EEEBz 38 1.495 DL-65 19 <2 BEEBz 30 1.491 DL-66 19 <2BEEEBz 30 1.492 DL-67 19 <2 2EHEBz 38 1.493 DL-68 19 <2 2EHEEBz 38 1.493DL-69 19 <2 DodBz 38 1.490 CL-22 11 <2 3GEH 75 1.466 DL-70 11 <2 EEEBz75 1.493 DL-71 11 <2 BEEBz 60 1.489 DL-72 11 <2 BEEEBz 60 1.488 DL-73 11<2 2EHEBz 75 1.490 DL-74 11 <2 2EHEEBz 75 1.489 DL-75 11 <2 DodBz 751.486

TABLE 20 Multilayer Interlayers with Benzoate Plasticizers Glass GlassMulti- Delta Refractive Transition Transition layer refractive index ofTemperature of Temperature of Inter- Skin Core Skin Plasti- indexinterlayer skin layers core layers layer layer 1 Layer layer 2 cizer(skin − core) (nD25) (° C.) (° C.) CI-22 CL-20 CL-21 CL-20 3GEH 0.0001.477 30 — CI-23 CL-20 CL-22 CL-20 3GEH 0.011 1.475 30 −2 DI-57 DL-64DL-70 DL-64 EEEBz 0.002 1.493 31 1 DI-58 DL-65 DL-71 DL-65 BEEBz 0.0021.491 29 −6 DI-59 DL-66 DL-72 DL-66 BEEEBz 0.004 1.491 31 −2 DI-60 DL-67DL-73 DL-67 2EHEBz 0.003 1.493 31 −3 DI-61 DL-68 DL-74 DL-68 2EHEEBz0.004 1.493 33 −1 DI-62 DL-69 DL-75 DL-69 DodBz 0.004 1.489 32 −4

As shown in Table 19 and 20, polyvinyl acetal resins comprising at leastone high refractive index benzoate plasticizer, including those EEEBz,BEEBz, BEEEBz, 2EHEBz, 2EHEEBz, and DodBz plasticizers listed above,tend to exhibit higher refractive indices than those comprising a lowerrefractive index plasticizer such as triethylene glycoldi-2-ethylhexanoate (3GEH). Additionally, as shown by comparison ofDisclosed Multilayer Interlayers DI-57 through DI-62, the higherrefractive index plasticizers used in these interlayer sheets give arefractive index difference of less than 0.010. The refractive index ofthe Disclosed Multilayer Interlayers, DI-57 through DI-62, as measuredby nD25 was at least 1.485 for all of the benzoate plasticizers andabove 1.490 for the EEEBz, BEEBz, BEEEBz, 2EHEBz, and 2EHEEBz benzoateplasticizers. The glass transition temperature of the core layers usingthe EEEBz, BEEBz, BEEEBz, 2EHEBz, 2EHEEBz, and DodBz plasticizers allremained at 1° C. or less.

Example 15: Mixed Benzoic Acid Based and Toluate Plasticizers with aHigh Refractive Index

Several mixed benzoic acid based plasticizers are listed by name withtheir abbreviation and refractive index as measured by nD25 in Table 15above. These mixed benzoic acid based plasticizers and toluateplasticizers can be mixed with poly(vinyl acetal) resins to producemonolayers, bilayers, and trilayers. The high refractive indexdemonstrated by these mixed benzoic acid and toluate based plasticizers,combined with the ability for greater uptake of these plasticizers bythe poly(vinyl acetal) resins with a lower residual hydroxyl content,can help minimize the difference in refractive indices between the coreand skin layers resulting in a less optical defects.

Dipropylene glycol di-o-toluate (DPGDT) and triethylene glycol benzoateacetate (TEGBzAc) were used to make Disclosed Interlayers DL-76 throughDL-79 in Table 21 below and these Disclosed Interlayers were used tomake Disclosed Multilayer Interlayers, DI-63 and DI-64, in Table 22below. Each Disclosed Multilayer Interlayers included a pair of outer“skin” layers, each having a thickness of 14 mils, sandwiching an inner“core” layer, having a thickness of 5 mils, formed by a resin having alower residual hydroxyl content.

TABLE 21 Mixed Benzoic Acid Based Plasticizers Residual Residual vinylRefractive hydroyxl acetate Plasticizer index of content content contentInterlayer Interlayer (wt. %) (wt. %) Plasticizers (phr) (nD25) CL-20 19<2 3GEH 38 1.477 DL 76 19 <2 DPGDT 38 1.497 DL 77 19 <2 TEGBzAc 30 1.490CL-22 11 <2 3GEH 75 1.466 DL-78 11 <2 DPGDT 75 1.500 DL 79 11 <2 TEGBzAc60 1.489

As shown in Tables 21 and 22, the poly(vinyl acetal) DisclosedInterlayers and Disclosed Multilayer Interlayers mixed with either theDPGDT or TEGBzAc mixed benzoate plasticizer resulted in a refractiveindex of at least 1.485 for the interlayer and resulting multilayerinterlayer. These refractive index values greater than 1.485 or 1.490for the poly(vinyl acetal) Disclosed Interlayers and DisclosedMultilayer Interlayers using DPGDT or TEGBzAc are relatively higher thanthe both poly(vinyl acetal) Comparative Interlayers and ComparativeMultilayer Interlayers utilizing 3GEH.

TABLE 22 Multilayer Interlayers with Mixed Benzoic Acid BasedPlasticizers Glass Glass Multi- Delta Refractive Transition Transitionlayer refractive index of Temperature of Temperature of Inter- Skin CoreSkin Plasti- index interlayer skin layers core layers layer layer 1Layer layer 2 cizer (skin − core) (nD25) (° C.) (° C.) CI-22 CL-20 CL-21CL-20 3GEH 0.000 1.477 30 — CI-23 CL-20 CL-22 CL-20 3GEH 0.011 1.475 30−2 DI-63 DL-76 DL-79 DL-76 DPGDT −0.003 1.493 36 8 DI-64 DL-77 DL-80DL-77 TEGBzAc 0.001 1.489 32 5

Example 16: Varying Core Layer Compositions with High Refractive IndexPlasticizers

Several different poly(vinyl butyral) resins or core layer compositionswere used to vary both the weight percent of residual hydroxyl contentand residual vinyl acetate in the polymer composition. Triethyleneglycol di-2-ethylhexanoate (3GEH) and bis-(butoxyethoxyethyl)terephthalate (BEETP) were the plasticizers added in different amountsto these core layer compositions to make Disclosed Interlayers DL-80 toDL-82. Again, the high refractive index demonstrated by theseterephthalate plasticizers, combined with the ability for greater uptakeof these plasticizers by the poly(vinyl acetal) resins with a lowerresidual hydroxyl content, can help minimize the difference inrefractive indices for the core and skin layers resulting in a lessoptical defects. The Comparative Interlayers, CL-20 to CL-24, andDisclosed Interlayers, DL-80 to DL-82, in Table 23 below were used tomake Comparative Multilayer Interlayers, CI-22 to CI-25, and DisclosedMultilayer Interlayers, DI-65 and DI-66, in Table 24 below. Eachmultilayer interlayer included a pair of outer “skin” layers, eachhaving a thickness of 14 mils, sandwiching an inner “core” layer, havinga thickness of 5 mils, formed by a resin having a lower residualhydroxyl content.

TABLE 23 Plasticizers Mixed with Different Core Layer CompositionsResidual Total Residual vinyl plasticizer hydroyxl acetate 3GEH BEETPcontent in Refractive Inter- content content content content each layerIndex layer (wt. %) (wt. %) (phr) (phr) (phr) (nD25) CL-20 19 <2 38 — 381.477 CL-21 19 <2 38 — 38 1.477 CL-22 11 <2 75 — 75 1.466 CL-23 12 18 75— 75 1.464 CL-24 12 12 75 — 75 1.465 DL-80 19 <2 — 38 38 1.477 DL-81 1218 — 75 75 1.487 DL-82 12 12 — 75 75 1.488

TABLE 24 Multilayer Interlayers with Different Core Compositions DeltaRefractive Glass Transition Multi- Refractive Index of Temperature layerIndex Multilayer (° C.) Loss Inter- Skin Core Skin Plasti- (skin layer −Interlayer Skin Core Factor layer layer 1 Layer layer 2 cizer 1 corelayer) (nD25) layer layer at 20° C. CI-22 CL-20 CL-21 CL-20 3GEH 0.0001.477 30 — 0.02 CI-23 CL-20 CL-22 CL-20 3GEH 0.011 1.475 30 −2 0.32CI-24 CL-20 CL-23 CL-20 3GEH n/a n/a 30 −4 0.36 CI-25 CL-20 CL-24 CL-203GEH n/a n/a 36.4 −3 0.31 DI-65 DL-80 DL-81 DL-80 BEETP n/a n/a 38.4 00.52 DI-66 DL-80 DL-82 DL-80 BEETP n/a n/a 37.2 1 0.54

As shown in Table 23 and 24, a glass transition temperature lower than2° C. can be achieved with different poly(vinyl acetal) resins.Additionally, poly(vinyl acetal) resins with different residual hydroxyland residual acetate content can be used to design interlayers andmultilayer interlayersfor low glass transition temperatures to improveacoustic and material properties such as sound transmission loss (STL).

Example 17: Making Resin Blends with High Refractive Index Plasticizers

Two polyvinyl n-butyral resins, Resin R-1 and Resin R-2, were preparedaccording to the procedure described above in Example 1. Resin R-1 had aresidual hydroxyl content of 19 weight percent, while resin R-2 had aresidual hydroxyl content of 11 weight percent. Both resins had residualacetate contents of 2 weight percent. Several resin blends were preparedthat included varying amounts of resins R-1 and R-2 in order to simulatevarious blending rates. To create the several blends presented in Table25 to Table 31, Resin R-1 and Resin R-2 are mixed together andplasticizer is added into the mixture and blended together. Thesecomponents are fed into a Brabender lab melt mixer and melt mixed at atemperature of 170° C. for 7 minutes. The resulting melt is taken outand pressed into a sheet having a thickness of about 0.76 mm in order toform resin layer samples that are then analyzed for Tan Delta, glasstransition temperature, HLD Haze, and refractive index as previouslydescribed.

Bis-(butoxyethyl) terephthalate (BETP), bis-(ethoxyethyl) terephthalate(EETP), dipropylene glycol di-o-toluate (DPGDT), triethylene glycolbenzoate acetate (TEGBzAc), butoxyethoxyethyl benzoate (BEEBz), dodecylbenzoate (DodBz), Bis-(ethoxyethoxyethyl) terephthalate (EEETP),bis-(methoxyethyl) terephthalate (METP), bis-(butoxyethoxyethyl)terephthalate (BEETP), were used to make each of the respectiveDisclosed Blended Layer DBL-29 through DBL-69 in Tables 25 to Table 31below. Disclosed Interlayers, DL-83 through DL-140, were additionallymade to compare the Tan Delta, glass transition temperature, HLD Haze,and refractive index for additional single resin Disclosed Interlayers.

TABLE 25 Resin Blends and Interlayers with Bis-(butoxyethyl)terephthalate (BETP) Plasticizer Resin Resin Inter- R-1 R-2 BETP Tg phrHLD layer (g) (g) (g) (° C.) of pz Haze RI DL-83 50 0 15 40 30 0.561.4915 DL-84 50 0 19 33.7 38 0.27 1.4913 DL-85 50 0 21.5 30.3 43 0.491.4910 DL-86 0 40 28 5.7 70 1.35 1.4870 DL-87 0 40 30 3.3 75 0.17 1.4867DL-88 0 40 34 −0.3 85 0.33 1.4866 DBL-29 48 2 17.5 40.1 35 0.84 1.4898DBL-30 48 2 20 32.5 40 1.01 1.4902 DBL-31 48 2 22.5 29.5 45 1.16 1.4904DBL-32 2 48 17.5 26.1 35 0.86 1.4870

TABLE 26 Resin Blends and Interlayers with Bis-(ethoxyethyl)terephthalate (EETP) and Bis-(butoxyethyl) terephthalate (BETP)Plasticizer Resin Resin Inter- R-1 R-2 EETP BETP phr Tg tan HLD layer(g) (g) (g) (g) of pz (° C.) Delta Haze DL-89 50 0 15 0 30 37 1.424 0.15DL-90 50 0 19 0 38 28.2 1.28 0.26 DL-91 50 0 21.5 0 43 25.1 1.209 0.41DL-92 0 40 28 0 70 3.76 1.487 0.3 DL-93 0 40 30 0 75 −0.48 1.34 0.23DL-94 0 40 34 0 85 −2.68 1.295 0.1 DBL-33 48 2 17.5 0 35 32.3 1.275 0.67DBL-34 48 2 20 0 40 28.3 1.311 0.7 DBL-35 48 2 22.5 0 45 25.9 1.149 0.57DBL-36 48 2 0 17.5 35 34.5 1.347 0.75 DBL-37 48 2 0 20 40 31.3 1.1890.49 DBL-38 48 2 0 22.5 45 29.1 1.104 0.9

TABLE 27 Resin Blends and Interlayer with Dipropylene glycoldi-o-toluate (DPGDT) Plasticizer Resin Resin Inter- R-1 R-2 DPGDT 3GEHphr HLD Tg tan layer (g) (g) (g) (g) of pz RI Haze (° C.) Delta DL-95 500 15 0 30 1.4974 0.28 41.8 1.53 DL-96 50 0 19 0 38 1.4990 0.09 35.7 1.36DL-97 50 0 21.5 0 43 1.4998 0.31 31.8 1.34 DL-98 0 40 28 0 70 1.50000.54 9.2 1.52 DL-99 0 40 30 0 75 1.5005 0.38 7.7 1.52 DL-100 0 40 34 085 1.5033 0.98 4.4 1.47 DBL-39 48 2 17.5 0 35 1.4981 0.57 38.3 1.38DBL-40 48 2 20 0 40 1.4989 0.41 34.3 1.29 DBL-41 48 2 22.5 0 45 1.49960.66 30.3 1.24 CL-25 0 40 0 30 75 1.4653 nd −5.4 1.11

TABLE 28 Resin Blends and Interlayers with Triethylene glycol benzoateacetate (TEGBzAc) Plasticizer Resin Resin Inter- R-1 R-2 TEGBzAc phr Tgtan HLD layer (g) (g) (g) of pz (° C.) Delta Haze DL-101 50 0 15 30 31.81.4 0.05 DL-102 50 0 19 38 24.9 1.27 0.04 DL-103 50 0 21.5 43 22 1.190.00 DL-104 0 40 26 65 3.4 1.31 0.03 DL-105 0 40 30 75 −0.8 1.25 0.10DL-106 0 40 34 85 −3 1.15 0.04 DBL-42 48 2 17.5 35 28 1.29 0.18 DBL-4348 2 20 40 24 1.22 0.52 DBL-44 48 2 22.5 45 20.1 1.17 0.36

TABLE 29 Resin Blends and Interlayers with Butoxyethoxyethyl benzoate(BEEBz) and Dodecyl benzoate (DodBz) Plasticizers Resin Resin Inter- R-1R-2 DodBz BEEBZ 3GEH Total Tg/ HLD layer (g) (g) (g) (g) (g) phr ° C. RIHaze DL-107 50 0 15 0 0 30 37.7 1.4898 0 DL-108 50 0 19 0 0 38 32.31.4897 0 DL-109 50 0 21.5 0 0 43 28.6 1.4894 0.03 DL-110 0 40 26 0 0 65−0.2 1.4868 0.25 DL-111 0 40 30 0 0 75 −4.1 1.4857 0.03 DL-112 0 40 34 00 85 −8.9 1.4851 0.38 DBL-45 48 2 17.5 0 0 35 35.2 1.4897 0.81 DBL-46 482 20 0 0 40 31.1 1.4876 0.93 DBL-47 48 2 22.5 0 0 45 28.3 1.4890 1.16DL-113 50 0 0 15 0 30 28.5 1.4910 0 DL-114 50 0 0 19 0 38 22.8 1.4917 0DL-115 50 0 0 21.5 0 43 19.2 1.4891 0.08 DL-116 0 40 0 26 0 65 −7.91.4878 0 DL-117 0 40 0 30 0 75 −14.1 1.4857 0.08 DL-118 0 40 0 34 0 85−15.1 1.4891 0.31 DBL-48 48 2 0 17.5 0 35 23.5 1.4928 0.27 DBL-49 48 2 020 0 40 19.8 1.4934 0.33 DBL-50 48 2 0 22.5 0 45 16.3 1.4933 0.48 DBL-5125 25 21.5 0 0 43 34.5 1.4907 14.3 DBL-52 25 25 0 21.5 0 43 21.6 1.49225.0 CL-26 25 25 0 0 21.5 43 33.7 1.4767 67.4

TABLE 30 Resin Blends with Bis-ethoxyethoxyethyl terephthalate (EEETP),Bis-methoxyethyl terephthalate (METP), and Bis-butoxyethoxyethylterephthalate (BEETP) Plasticizers Resin Resin Inter- R-1 R-2 BEETPEEETP 3GEH Total Tg/ HLD layer (g) (g) (g) (g) METP (g) phr ° C. Haze RIDL-119 50 0 15 0 0 0 30 38.5 0 1.4934 DL-120 50 0 19 0 0 0 38 32 01.4931 DL-121 50 0 21.5 0 0 0 43 28.8 0.46 1.4913 DL-122 0 40 26 0 0 065 6.5 0.09 1.4888 DL-123 0 40 30 0 0 0 75 1 0.13 1.4888 DL-124 0 40 340 0 0 85 −1.5 0 1.4862 DBL-53 48 2 17.5 0 0 0 35 35.3 0.38 1.4917 DBL-5448 2 20 0 0 0 40 31.7 0.63 1.4927 DBL-55 48 2 22.5 0 0 0 45 27.6 0.561.4917 DL-125 50 0 0 15 0 0 30 36.8 0.02 1.4945 DL-126 50 0 0 19 0 0 3831.4 0.12 1.4965 DL-127 50 0 0 21.5 0 0 43 27.1 0.21 1.4965 DL-128 0 400 26 0 0 65 4.7 0.31 1.4899 DL-129 0 40 0 30 0 0 75 0.8 0.09 1.4899DL-130 0 40 0 34 0 0 85 — 0.53 — DBL-56 48 2 0 17.5 0 0 35 — 0.48 1.4928DBL-57 48 2 0 20 0 0 40 — 0.16 1.4942 DBL-58 48 2 0 22.5 0 0 45 — 0.701.4918 DL-131 50 0 0 0 15 0 30 36.2 0 1.4980 DL-132 50 0 0 0 19 0 3829.5 0.02 1.4942 DL-133 50 0 0 0 21.5 0 43 25.4 0 1.4999 DL-134 0 40 0 026 0 65 4.8 0 1.4951 DL-135 0 40 0 0 30 0 75 0 0.06 1.4938 DL-136 0 40 00 34 0 85 −2.4 0.44 1.4951 DBL-59 48 2 0 0 17.5 0 35 31.5 0.20 1.4979DBL-60 48 2 0 0 20 0 40 27.2 0.16 1.4948 DBL-61 48 2 0 0 22.5 0 45 24.20.46 1.4931 DBL-62 25 25 21.5 0 0 0 43  1.8, 37.1 12.66 1.4848 DBL-63 2525 0 21.5 0 0 43 10.0, 27.1 5.55 1.4900 DBL-64 25 25 0 0 21.5 0 43 12.2,26.5 4.06 1.4937 CL-27 25 25 0 0 0 21.5 43 −4.1, 38.9 125.78 1.4753

Example 18: Making Resin Blend Sheets with High Refractive IndexPlasticizers

Two polyvinyl n-butyral resins, Resin R-1 and Resin R-2, were preparedaccording to the procedure described above in Example 1. Resin R-1 had aresidual hydroxyl content of 19 weight percent, while resin R-2 had aresidual hydroxyl content of 11 weight percent. Both resins had residualacetate contents of 2 weight percent. These components are fed into aBrabender lab melt mixer and melt mixed at a temperature of 170° C. for7 minutes. The resulting melt is taken out and pressed into a sheethaving a thickness of about 30 guage in order to form resin layersamples. Two resin layers were prepared for each of the triethyleneglycol di-2-ethylhexanoate (3GEH), bis-(butoxyethyl) terephthalate(BETP), bis-(butoxyethoxyethyl) terephthalate (BEETP), butoxyethoxyethylbenzoate (BEEBz), dodecyl benzoate (DodBz) plastcizers. The first layerwas entirely Resin R-1 with the respective plasticizer and the secondlayer was 96 parts Resin R-1 and 4 parts Resin R-2 with the samerespective plasticizer. The resin layer samples were analyzed for Hazeand Visible light transmittance.

TABLE 31 Sheets of Resin Blends with Plasticizer Sheet Composition andProperty 3GEH BETP BEETP BEEBz DodBz PVB sheet No. CL-28 CBL-18 DL-137DBL-65 DL-138 DBL-66 DL-139 DBL-67 DL-140 DBL-68 Parts by wt. PVB 100 96100 96 100 96 100 96 100 96 Resin R-1 Parts by wt. PVB 0 4 0 4 0 4 0 4 04 Resin R-2 plasticizer content 40 40 40 40 40 40 40 40 40 40 (phr) Haze(%) 0.3 1.9 0.3 0.4 0.4 0.4 0.4 0.4 0.3 0.4 Visible light 87.8 84.6 87.887.7 87.7 87.9 88 87.8 87.8 87.6 transmittance (%)

As shown in Table 31, above, blended poly(vinyl acetal) resin layers orinterlayers formed with 3GEH exhibit increased optical defects, asindicated by a haze percentage greater than 1. The blended poly(vinylacetal) resin layer or interlayer formed with BETP, BEETP, BEEBz, andDodBz, DBL-65 through DBL-68, exhibit less optical defects as indicatedby a haze percentage less than 1. Additionally, the blended poly(vinylacetal) Disclosed Interlayers formed with BETP, BEETP, BEEBz, and DodBz,DBL-65 through DBL-68, have the same haze value as the single resinpoly(vinyl acetal) Disclosed Interlayers DL-137 through DL-140. Theblended poly(vinyl acetal) Disclosed Interlayers formed with BETP,BEETP, BEEBz, and DodBz show less of a difference in visible lighttransmittance than the CL-28 and CBL-18 examples using 3GEH.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. For example, an interlayer canbe formed comprising poly(vinyl butyral) having a residual hydroxylcontent in any of the ranges given in addition to comprising aplasticizers in any of the ranges given to form many permutations thatare within the scope of the present disclosure, but that would becumbersome to list. Further, ranges provided for a genus or a category,such as phthalates or benzoates, can also be applied to species withinthe genus or members of the category, such as dioctyl terephthalate,unless otherwise noted.

What is claimed is:
 1. A blended resin composition comprising: a firstpoly(vinyl acetal) resin comprising a residual hydroxyl content; asecond poly(vinyl acetal) resin comprising a residual hydroxyl content;and at least one plasticizer having a refractive index of at least 1.460to about 1.520; wherein the residual hydroxyl content of said secondpoly(vinyl acetal) resin is at least 2 weight percent lower than theresidual hydroxyl content of said first poly(vinyl acetal) resin,wherein said first poly(vinyl acetal) resin comprises residues of afirst aldehyde and said second poly(vinyl acetal) resin comprisesresidues of a second aldehyde, and wherein said first and said secondaldehydes have the same number of carbon atoms per molecule, whereinsaid second poly(vinyl acetal) resin is present in said blended resincomposition in an amount of not more than about 12 weight percent, basedon the total weight of said first and said second poly(vinyl acetal)resins, and wherein said blended resin composition has a haze value ofless than about 1 percent.
 2. The blended resin composition of claim 1,wherein each of said first and said second aldehydes aren-butyraldehyde.
 3. The blended resin composition of claim 1, whereineach of said first and said second poly(vinyl acetal) resin componentsare present in said blended resin composition in an amount of at least0.3 weight percent, based on the total weight of all resins in saidcomposition.
 4. The blended resin composition of claim 1, wherein saidplasticizer comprises at least one of the following compounds:bis-(methoxyethyl) terephthalate, bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(2-ethylhexyloxyethyl)terephthalate, bis-(2-ethylhexyl) iso-phthalate,bis-(2-ethylhexyloxyethoxyethyl) terephthalate, 2-ethylhexyloxyethylbenzoate, 2-ethylhexyloxyethoxylethyl benzoate, ethoxyethoxyethylbenzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate,dodecyl benzoate, dipropylene glycol di-o-toluate, triethylene glycolbenzoate acetate, trioctyl trimellitate, or combinations thereof.
 5. Theblended resin composition of claim 1, wherein said plasticizer comprisesat least one of the following compounds: bis-(methoxyethyl)terephthalate, bis-(butoxyethyl) terephthalate, bis-(butoxyethoxyethyl)terephthalate, bis-(ethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl)terephthalate, bis-(2-ethylhexyloxyethyl) terephthalate,bis-(2-ethylhexyl) iso-phthalate, ethoxyethoxyethyl benzoate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, dodecylbenzoate, dipropylene glycol di-o-toluate, triethylene glycol benzoateacetate, trioctyl trimellitate, or combinations thereof.
 6. The blendedresin composition of claim 1, wherein said plasticizer comprises atleast one of the following compounds: bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(2-ethylhexyl) iso-phthalate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, dodecylbenzoate, dipropylene glycol di-o-toluate, triethylene glycol benzoateacetate, trioctyl trimellitate, or combinations thereof.
 7. The blendedresin composition of claim 1, wherein said plasticizer is present insaid blended resin composition in an amount in the range of from 10 to100 phr, and wherein said blended resin composition has a refractiveindex of at least 1.480 and a glass transition temperature of not morethan 25° C.
 8. The blended resin composition of claim 1, wherein saidplasticizer is present in said blended resin composition in an amount inthe range of from 30 to 90 phr, and wherein said blended resincomposition has a refractive index of at least 1.480 and a glasstransition temperature of not more than 25° C.
 9. The blended resincomposition of claim 1, wherein said plasticizer is present in saidresin composition in an amount in the range of from 5 to 50 phr andwherein said resin composition has a refractive index of at least 1.480and a glass transition temperature of at least 26° C.
 10. A multiplelayer panel comprising at least one rigid substrate and at least oneresin layer formed from said blended resin composition of claim
 1. 11. Aresin composition comprising: a blended poly(vinyl acetal) resincomprising: a first poly(vinyl acetal) resin comprising a residualhydroxyl content, wherein said first poly(vinyl acetal) resin comprisesresidues of a first aldehyde; a second poly(vinyl acetal) resincomprising a residual hydroxyl content, wherein said second poly(vinylacetal) resin comprises residues of a second aldehyde; and at least oneplasticizer having a refractive index of at least 1.460 to about 1.520,wherein the residual hydroxyl content of said second poly(vinyl acetal)resin is at least 2 weight percent lower than the residual hydroxylcontent of said first poly(vinyl acetal) resin and wherein said firstand said second aldehydes have the same number of carbon atoms permolecule, wherein said second poly(vinyl acetal) resin is present insaid blended poly(vinyl acetal) resin in an amount of not more thanabout 12 weight percent, based on the total weight of said first andsaid second poly(vinyl acetal) resins, and wherein said blendedpoly(vinyl acetal) resin has a haze value of less than about 1 percent.12. The resin composition of claim 11, wherein said plasticizercomprises at least one of the following compounds: bis-(methoxyethyl)terephthalate, bis-(butoxyethyl) terephthalate, bis-(butoxyethoxyethyl)terephthalate, bis-(ethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl)terephthalate, bis-(2-ethylhexyloxyethyl) terephthalate,bis-(2-ethylhexyl) iso-phthalate, bis-(2-ethylhexyloxyethoxyethyl)terephthalate, 2-ethyl hexyloxyethyl benzoate, 2-ethylhexyloxyethoxylethyl benzoate, ethoxyethoxyethyl benzoate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, dodecylbenzoate, dipropylene glycol di-o-toluate, triethylene glycol benzoateacetate, trioctyl trimellitate, or combinations thereof.
 13. The resincomposition of claim 11, wherein said plasticizer comprises at least oneof the following compounds: bis-(methoxyethyl) terephthalate,bis-(butoxyethyl) terephthalate, bis-(butoxyethoxyethyl) terephthalate,bis-(ethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl) terephthalate,bis-(2-ethylhexyloxyethyl) terephthalate, bis-(2-ethylhexyl)iso-phthalate, ethoxyethoxyethyl benzoate, butoxyethoxyethyl benzoate,butoxyethoxyethoxyethyl benzoate, dodecyl benzoate, dipropylene glycoldi-o-toluate, triethylene glycol benzoate acetate, trioctyltrimellitate, or combinations thereof.
 14. The resin composition ofclaim 11, wherein said plasticizer comprises at least one of thefollowing compounds: bis-(butoxyethyl) terephthalate,bis-(butoxyethoxyethyl) terephthalate, bis-(ethoxyethyl) terephthalate,bis-(ethoxyethoxyethyl) terephthalate, bis-(2-ethylhexyl) iso-phthalate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, dodecylbenzoate, dipropylene glycol di-o-toluate, triethylene glycol benzoateacetate, trioctyl trimellitate, or combinations thereof.
 15. The resincomposition of claim 11, wherein each of said first and said secondaldehydes are n-butyraldehyde.
 16. The resin composition of claim 11,wherein each of the first and second poly(vinyl acetal) resins arepresent in said blended poly(vinyl acetal)_resin in an amount of atleast 0.3 weight percent, based on the total weight of resins in saidblended poly(vinyl acetal)_resin and wherein the combined amount of saidfirst and said second poly(vinyl acetal) resins comprise at least about80 weight percent of the total weight of all resins in said blendedpoly(vinyl acetal)_resin.
 17. A method for making an interlayer, saidmethod comprising: (a) providing a first poly(vinyl acetal) resincomprising a residual hydroxyl content, wherein said first poly(vinylacetal) resin comprises residues of a first aldehyde; (b) providing asecond poly(vinyl acetal) resin comprising a residual hydroxyl content,wherein said second poly(vinyl acetal) resin comprises residues of asecond aldehyde; (c) blending said first poly(vinyl acetal) resin andsaid second poly(vinyl acetal) resin and at least one plasticizer havinga refractive index of at least 1.460 to about 1.520 to form a blendedplasticized poly(vinyl acetal) resin; and (d) forming at least one resinlayer comprising said blended plasticized poly(vinyl acetal) resin;wherein the residual hydroxyl content of said second poly(vinyl acetal)resin is at least 2 weight percent lower than the residual hydroxylcontent of said first poly(vinyl acetal) resin, and wherein said firstand said second aldehydes have the same number of carbon atoms permolecule, and wherein said second poly(vinyl acetal) resin is present insaid blended plasticized poly(vinyl acetal) resin in an amount of notmore than about 12 weight percent, based on the total weight of saidfirst and said second poly(vinyl acetal) resins, and wherein saidblended plasticized poly(vinyl acetal) resin has a haze value of lessthan about 1 percent.
 18. The method of claim 17, wherein saidplasticizer comprises at least one of the following compounds:bis-(butoxyethyl) terephthalate, bis-(butoxyethoxyethyl) terephthalate,bis-(ethoxyethyl) terephthalate, bis-(ethoxyethoxyethyl) terephthalate,bis-(2-ethylhexyl) iso-phthalate, butoxyethoxyethyl benzoate,butoxyethoxyethoxyethyl benzoate, dodecyl benzoate, dipropylene glycoldi-o-toluate, triethylene glycol benzoate acetate, trioctyltrimellitate, or combinations thereof.
 19. The blended resin compositionof claim 1, wherein said plasticizer comprises a blend of two or moreplasticizers.
 20. The resin composition of claim 1, wherein saidplasticizer comprises a blend of two or more plasticizers.